Reference distribution bus

ABSTRACT

A system that includes a multiplexer having an output selectively coupled to a plurality of inputs, a bus coupled to the output of the multiplexer, and first and second circuits configured to generate first and second digital signals, respectively. The first digital signal is related to a rotational angle of a crankshaft at a first point in time, and the second digital signal is related to a value of parameter at the first point in time, wherein the parameter is one other than the rotational angle of the crankshaft. The first and second circuits are coupled directly or indirectly to first and second inputs of the multiplexer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/264,538; filed on Nov. 4, 2008; entitled “Digital I/O SignalScheduler,” naming Samuel J. Guido, Jeremy W. Brodt, and Jeffrey T.Sieber as inventors, and is incorporated by reference herein in itsentirety and for all purposes.

BACKGROUND OF THE INVENTION

Modern control systems are growing in application and complexity. Thereare many classes of control systems, with many variations andcombinations. Some control systems generate signals that controlcomponents. For example, some automobile engine control systems generatesignals that directly or indirectly control various components (e.g.,spark plugs, fuel injectors, etc.) of an internal combustion engine. Thepresent invention will be described with reference to an automobileengine control system, it being understood that the present inventionshould not be limited thereto.

The simplest engine control systems only control the timing and quantityof fuel injected into each cylinder during each cycle of the engine.More advanced engine control systems found in modern cars also controlignition timing, variable valve timing, the level of boost maintained bya turbo charger, etc. Using a complex set of algorithms, engine controlsystems can determine the quantity and timing of fuel injected intocylinders, ignition timing, and other needed parameters by monitoringthe engine through sensors that include, for example, a manifoldabsolute pressure sensor, throttle position sensor, air temperaturesensor, oxygen sensor, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood in its numerous objects,features, and advantages made apparent to those skilled in the art byreferencing the accompanying drawings.

FIG. 1 illustrates in block diagram form, relevant components of anexample control system.

FIG. 2 is a timing diagram that illustrates example reference valuesthat are received by the reference-bus controller of the control systemshown in FIG. 1.

FIG. 3 illustrates in block diagram form, relevant components of anexample reference-bus controller employed the control system shown inFIG. 1.

FIG. 4 represents an example transfer of reference values over thereference-bus of FIG. 1.

FIG. 5 illustrates in block diagram form, relevant components of anexample event-bus employed in the control system shown in FIG. 1.

FIG. 6 illustrates in block diagram form, relevant components of anexample I/O circuit employed in the control system shown in FIG. 1.

FIG. 7 illustrates relevant components of an example timer circuitemployed in the control system shown in FIG. 1.

FIG. 8 illustrates the timer circuit of FIG. 7 with a more detailed viewof a reference match circuit thereof.

FIG. 9 illustrates relevant operational aspects of an example processperformed by the reference match circuit of FIG. 8.

FIGS. 10A and 10B show example timing diagrams of a match-signalgenerated by the reference match circuit of FIG. 8 as it operatesaccording to the process shown in FIG. 9.

FIG. 11 illustrates in block diagram form, relevant components of anexample input exception (IE) circuit employed in the timer circuit ofFIGS. 7 and 8.

FIGS. 12A-12F are timing diagrams that show relevant aspects of an eventlogic circuit's operation in response to assertion of example IEcommands.

FIG. 13 illustrates relevant components of an example analog comparatorcircuit employed in the control system of FIG. 1.

FIG. 14 illustrates timer and I/O circuits employed in the controlsystem shown in FIG. 1, which are configured to generate an examplespark signal.

FIG. 15 illustrate example timing diagrams for the event-signals andspark signal that are generated by the timer and I/O circuits shown inFIG. 13.

FIG. 16 illustrates relevant components of an example analog comparatorthat could be used in instead of one of the timer circuits shown in FIG.14.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DETAILED DESCRIPTION

The present invention relates to a control system. For purposes ofexplanation only, the present invention will be described with referenceto a control system for controlling an automobile engine. Moreparticularly, the present invention will be described with reference toa control system that directly or indirectly controls multiplecomponents of an automobile engine such as fuel injectors, spark plugcoils, etc., it being understood that the present invention may alsofind application in controlling components of other devises suchtransmissions, boat engines, motors employed in manufacturing equipment,internal combustion engines that generate electricity for driving anelectric motor of an automobile, etc.

Control System Overview

FIG. 1 illustrates in block diagram form, relevant components of anexample control system 10. The various components of the control system10 shown in FIG. 1 may be implemented as one or more integrated circuitsformed on one or more integrated circuit substrates. When implemented onseparate substrates, the integrated circuits can be coupled togetherusing electrically conductive traces on a printed circuit board. Theterm coupled should not be limited to a direct connection betweencomponents; two devices can be coupled together via one or moreintervening devices.

Control system 10 generates control signals that control respectiveengine components. For example, control system 10 generates a one-bitcontrol signal for controlling a coil circuit 12, which in turn controlsthe flow of current into a spark plug coil 16. Control system 10 alsogenerates another one-bit control signal for controlling a fuel injector14, which in turn controls the flow of fuel into an engine cylinder (notshown). The example one-bit control signal that controls coil circuit 12will hereinafter be referred to as the “spark signal,” and the exampleone-bit control signal that controls fuel injector 14 will hereinafterbe referred to as the “fuel signal.”

The present invention will be described with reference to control system10 generating spark and fuel signals. However the example control system10 can generate several additional spark signals for controllingrespective coil circuits, several additional fuel signals forcontrolling respective fuel injectors, and several other control signalsfor controlling other engine components (not shown). Further, while thepresent invention will be described with reference to control system 10generating one-bit control signals, it is understood the presentinvention should not be limited thereto. In another embodiment, multibitcontrol signals may be generated for controlling components that operatein more than two modes. Single bit signals, such as the exemplary sparkor fuel signal, are either “ON” (i.e., asserted, active or has voltagelevel equal to Vdd) or “OFF” (i.e., unasserted, inactive or a voltagelevel equal to ground).

With continuing reference to FIG. 1, coil circuit 12 controls currentflow to coil 16, which in turn is coupled to a spark plug 22. Coilcircuit 12 selectively provides current for charging coil 16, which inturn provides the energy that is used by spark plug 22 for creating aspark within an engine cylinder (not shown). When the spark signal isON, current flows into coil 16, and when the spark signal is OFF, nocurrent flows into coil 16.

Current sensor 20 generates an analog signal representing the quantityof current I flowing into coil 16. At regularly scheduled times,analog/digital convertor 24 samples and converts this analog signal intoa multibit digital value V1t. Use of the letter “t” indicates the valuechanges over time. Thus, V1t is a multibit value representing thequantity of current flowing into coil 16. V1t is provided back tocontrol system 10, and the state of the spark signal generated bycontrol system 10, may depend on V1t as will be more fully describedbelow.

In addition to generating the spark signal, control system 10 maygenerate the fuel signal for controlling fuel injector 14. In responseto receiving the fuel signal, fuel injector 14 selectively injects fuelinto an engine cylinder (not shown). When the fuel signal is ON,injector 14 injects fuel into its cylinder, and when the fuel signal isOFF, injector 14 does not inject fuel into the cylinder. Coil circuit 12and fuel injector 14 are examples of many different types of componentsthat can be controlled by control system 10.

With continuing reference to FIG. 1, control system 10 includes timercircuits 30 coupled to each other, I/O circuits 32, and analog signalcomparator (ASC) circuits 33 via event-bus 34. I/O circuits 32 and ASCcircuits 33 are coupled to I/O pins 35 and 36 as shown.

Event-bus 34 is controlled by an event-bus controller 38, which will bemore fully described below. As will be more fully described below,event-bus 34 may take form in serial and parallel sub-buses, it beingunderstood the present invention should not be limited thereto.

FIG. 1 shows a single event-bus 34 that couples all timer circuits 30,I/O circuits 32, and ASC circuits 33. In an alternative embodiment, twoor more event-buses may be used to couple selective timer circuits 30,I/O circuits 32, and ASC circuits 33. For example a one event-bus (notshown) could couple timer circuits 30-1-30-10, I/O circuits 32-1-32-5and ASC circuits 33-1-33-3, while a another event-bus (not shown) couldcouple timer circuits 30-11-30-20, I/O circuits 32-6-32-8 and ASCcircuits 33-3-33-6. Alternatively, one event-bus (not shown) couldcouple timer circuits 30-1-30-8 and I/O circuits 32-1-32-4, whileanother event-bus (not shown) could couple timer circuits 30-9-30-40,I/O circuits 32-5-32-8 and ASC circuits 33-1-33-5. In these alternativeembodiments, each event-bus may be controlled by a respective event-buscontroller. The present invention, however, will be described withreference to a single event-bus 34 and a single event-bus controller 38as shown in FIG. 1.

Timer circuits 30, I/O circuits 32, and ASC circuits 33 areprogrammable. When programmed, timer circuits 30 generate one-bitevent-signals, which are selectively transmitted to each other and toI/O circuits 32 via event-bus 34. Likewise, ASC circuits 33 whenprogrammed generate one-bit event-signals, which are selectivelytransmitted to timer circuits 30 via event-bus 34. An event-signal, asits name implies, indicates that some event has occurred, should occur,or is occurring. For example, an event-signal ES-5 may indicate thatcurrent I supplied to coil 16 has exceeded a predetermined value, whilean event-signal ES-20 may indicate that fuel injector 14 should injectfuel into its engine cylinder. An event-signal is either ON or OFF.

Event-signals can be transmitted concurrently with respective multibitevent identifiers (event-IDs). Alternatively, event-signals can betransmitted after transmission of respective multibit event-IDs. Thepresent invention will be described with reference to concurrenttransmission of event-signals and their respective multibit event-IDs.

When a timer circuit (e.g., timer circuit 30-1) transmits itsevent-signal (e.g., event-signal “ES-1”), the timer circuit mayconcurrently transmit a respective event-ID (e.g., event-ID “SPARK”) tothe other timer circuits and to the I/O circuits 32 via event-bus 34.Likewise, when an ASC circuits 33 (e.g., ASC circuit 33-1) transmits itsevent-signal (e.g., event-signal “ES-I”), the ASC circuit 33 mayconcurrently transmit a respective event-ID (e.g., event-ID “MAX”) tothe timer circuits 33 via event-bus 34. There is a one-to-one mapping ofevent-IDs to event-signals. An event-ID, as its name implies, identifiesits respective event-signal. In the embodiment shown in FIG. 1,event-bus 34 transmits one event-signal/event-ID pair at a time. Whenmore than one event-bus is used in the alternative embodiment brieflydescribed above, the event-buses may simultaneously transmit respectiveevent-signals/event-ID pairs. Again, the present invention will bedescribed with reference to a single event-bus 34.

While an event-signal and its respective event-ID may be concurrentlytransmitted to all timer circuits 30 and I/O circuits 32, one, some,none, or all of the timer circuits 30 and I/O circuits 32 may ignore theevent-signal as will be more fully described below. Importantly, I/Ocircuits 32 can generate control signals, such as the spark signal andthe fuel signal mentioned above, as a function of event-signals as willbe more fully described below. Also, the state of one timer circuit'sevent-signal (e.g., ES-1) may be affected by the state of another timercircuit's event-signal (e.g., ES-5) and/or by the state of an ASCcircuit 33's event-signal as will be more fully described below.

Control system 10 includes a device for programming or reprogrammingtimer circuits 30, I/O circuits 32, and ASC circuits 33. In theillustrated example, this programming device is a central processingunit (CPU) 40, which is in data communication with timer circuit 30, I/Ocircuits 32, and ASC circuits 33 via communication path 42, althoughFIG. 1 does not show CPU 40 in data communication with I/O circuits 32and ASC circuits 33. CPU 40 programs or reprograms timer circuits 30,I/O circuits 32 and/or ASC circuits 33 via communication path 42.Although not shown communication path 42 may include many distinctcomponents including, for example, memory management units, crossbars,bridges, direct memory access controllers, etc., to facilitate thetransfer of programming values to timer circuits 30, I/O circuits 32and/or ASC circuits 33. It should be noted that CPU 40 may also programother devices not shown in FIG. 1.

CPU 40 programs or reprograms timer circuits 30, I/O circuits 32 and ASCcircuits 33 with digital values such as operational parameters,input-exception codes (IE codes), comparator values, or event-IDs. Aswill be more fully described below, timer circuits 30, I/O circuits 32and ASC circuits 33 operate according to their programmed values (e.g.,operational parameters, comparator values, IE codes, or event-IDs). CPU40 generates one or more operational parameters and/or comparator valuesas a function of multibit engine control and/or status values such asengine speed, engine load, etc. More particularly, CPU 40 processesengine control and/or status values to generate operational parametersand/or comparator values in accordance with software instructions storedwithin memory 44. CPU 40 also selects IE codes, additional operationalparameters, additional comparator values or event-IDs for the timercircuits 30 and I/O circuits 32 in accordance with the softwareinstructions that CPU 40 executes. The software instructions also giveCPU 40 the intelligence to decide which of the timer circuits 30, I/Ocircuits 32 and ASC circuits 33 are to be programmed or reprogrammed.

Timer circuits 30 are programmed or reprogrammed when they receive andstore operational parameters, IE codes, and event-IDs. CPU 40 mayreprogram some or all of timer circuits 30 with replacement operationalparameters, IE codes, or event-IDs as CPU 40 receives and processes newengine control and/or status signals. Any one of the timer circuits 30can operate in any one of many different ways depending on theoperational parameters and IE codes they receive and store. In theembodiment shown, I/O circuits 32 and ASC circuits 33 are not programmedwith operational parameters or IE codes.

Control system 10 shows timer circuits 30 coupled to a reference-buscontroller 50 via a reference-bus 46. As will be more fully describedbelow, reference-bus controller 50 transmits multibit reference values(e.g., V1t from A/D convertor 24) in sequential order to some or alltimer circuits 30 via reference-bus 46. The reference values typicallychange over time in magnitude. The state of an event-signal generated bya timer circuit 30 may depend on one or more reference values as will bemore fully described below. It is noted reference-bus 50 may take formin one or more serial or parallel sub-buses. For the purposes ofexplanation only, it will be presumed that reference-bus 46 takes formin a parallel data bus.

In the example embodiment of FIG. 1, reference-bus controller 50captures and subsequently transmits three different types of referencevalues including (1) one or more time domain reference values, (2) oneor more angle domain reference values, and (3) one or more sensor domainreference signals, it being understood that the present invention couldbe implemented with fewer or more than three different types ofreference values. For the purposes of explanation only, the presentinvention will be described with reference-bus controller 50 capturingand subsequently transmitting (1) at least one time domain referencevalue Tt (2) at least two angle domain reference values FRAt and 720At,and (3) p sensor domain reference values V1t-Vpt. Reference valueschange in value over time. It should be noted that angle domainreferences are not limited to FRAt and 720At.

In the illustrated embodiment, time domain reference value Tt will takeform in a multibit output value of a sequential counter (not shown) attime t. The counter increments Tt by 1 with each cycle or half cycle ofa square wave clock signal input. FIG. 2 is a timing diagram thatillustrates an exemplary Tt. The counter begins with Tt set to 0 andincrements Tt by 1 with each full or half clock cycle until Tt reaches apredetermined value (e.g., 0xFFFFFF). Thereafter Tt returns to 0 andcontinues incrementing as shown. It is noted that the square wave clocksignal used by the counter may be a system clock provided to and used byeach of the components of control system 10 shown in FIG. 1.

FRAt (also known as the free running angle) and 720At (also known as the720 angle) are multibit angle domain reference values. 720At relates toan angular position of an engine cycle at time t. Reference values FRAtand 720At may be generated as a function of a variable reluctance sensor(not shown) output. A number of equally-spaced and equally-sized teethare formed around a crankshaft (not shown); two of the teeth, however,have a different distance between them. The sensor is located inproximity and senses the teeth as they pass. A processor (not shown)generates a predetermined number of “ticks” between sensed teeth basedon the sensor output. These ticks represent the resolution of the anglereference values FRAt and 720At. Ticks may have a resolution of 0.1degree, 0.25 degree, 0.5 degree, etc., of crankshaft rotation. When atooth is sensed, the period from the just previously sensed tooth, isused to generate ticks for the currently sensed tooth. Sinceacceleration and deceleration of the crankshaft can cause a tooth periodto be longer or shorter than the previous tooth period, the processorensures the correct number of ticks is produced for each tooth. This isdone by incrementing ticks quickly or by stopping them until the nexttooth is sensed. The two teeth that have a different distance betweenthem, as noted above, are used to identify a full rotation of thecrankshaft.

The ticks are provided to an angle reference value generator (not shown)that generates the angle reference values FRAt and 720At. The timingdiagram of FIG. 2 graphically illustrates exemplary angle domainreference values FRAt and 720At. Free running angle reference value FRAtis a multibit value between 0 and a predetermined number (e.g.,0xFFFFFF). FRAt may take form in the output of a first counter thatincrements with each tick or with each of a set number of ticks itreceives. The first counter increments FRAt by 1 until it reaches0xFFFFFF. Thereafter FRAt returns to 0 and continues incrementing asshown in FIG. 2. 720 angle reference value 720At is a multibit valuerepresenting a value between 0 and 720. 720At may take form in theoutput of a second counter that increments with each tick or with eachof a set number of ticks it receives. The second counter increments720At by 1 until it reaches 720. Thereafter 720At returns to 0 andcontinues incrementing as shown in FIG. 2. The second counter operatesin cycles, and in each cycle 720At increments from 0 to 720. The 720angle reference 720At increments from 0 to 720 with two full rotationsof the crankshaft, which is often referred to as a full engine cycle.

When the crankshaft rotation of speed increases or decreases, the rateat which the angle domain reference values increment increase ordecrease proportionally. To illustrate, assume the crankshaft rotates ata faster speed during the time period between t1 and t2 when compared tothe time period between t0 and t1. FIG. 2 shows that during the timeperiod between t1 and t2, 720At increments at a rate that is greaterthan the rate it increments during the time period between t0 and t1.

V1t-Vpt are referred to herein as sensor domain reference values, whichare multibit digital equivalents of respective analog signals generatedby, for example, various sensors within the engine at time t. Forexample, reference value V1t is a multibit digital signal equivalent ofthe analog signal generated by current sensor 20 (see FIG. 1), which inturn represents the quantity of current I flowing into coil 16 at timet.

Reference-Bus and Reference-Bus Controller

With continuing reference to FIGS. 1 and 2, FIG. 3 illustrates in blockdiagram form, relevant components of an example reference-bus controller50. As shown, reference-bus controller 50 includes a multiplexer 60coupled between reference-bus 46 and registers 62. Reference-buscontroller 50 also includes a logic control circuit 64 that controlsmultiplexer 60 and registers 62.

Registers 62 capture multibit reference values pending at theirrespective inputs in response to assertion of a one-bit register controlsignal rcs by control circuit 64. Thus, registers 62-1-62-q capturereference values Ts, FRAs, 720As, and V1s-Vps, respectively, which arepending at their inputs at the point in time s when control signal rcsis asserted. Any existing references value in registers 62 areoverwritten with new reference values.

Multiplexer 60, as its name implies, multiplexes the contents ofregisters 62 onto reference-bus 46 for subsequent transmission to alltimer circuits 30. The reference values of registers 62 are multiplexedonto reference-bus 46 and transmitted to timer circuits 30 in sequentialorder, beginning with the reference value stored in register 62-1 andending with the reference value stored in register 62-q, in accordancewith a multiplex control signals generated by logic control circuit 64.After the reference value of register 62-q is transmitted, the processrepeats: (1) logic control circuit asserts control signal rcs, (2)registers 62 capture the reference values that are pending at theirrespective inputs at the time when control signal rcs is asserted, and(3) multiplexer 60 multiplexes the reference values of registers 62 inorder, beginning with the reference value of register 62-1 and endingwith the reference value of register 62-q. FIG. 4 is a timing diagramthat shows an example transmission of reference values by reference-buscontroller 50 to timer circuits 30 over reference-bus 46. As seen,reference-bus 46 sequentially transmits a first set of reference values,beginning with T1 and ending with Vp1, each of which were stored inrespective registers 62 at time t=1. After the first set is transmitted,reference-bus 46 sequentially transmits a second set of referencevalues, beginning with T2 and ending with Vp2, each of which werecaptured by respective registers 62 at later time t=2. This processcontinues until logic control circuit 64 receives a stop command.

As will be more fully described below, timer circuits 30 store thereference values Ts, FRAs, 720As, and V1s-Vps they receive. In analternative embodiment, an additional register 62-q+1 (not shown) may beprovided that stores a non-changing SYNC value, which is multiplexedonto reference-bus 46 after the reference value of register 62-q ismultiplexed onto reference-bus 46. In this alternative embodiment,control circuit 64 asserts register control signal res when the SYNCvalue is multiplexed onto the reference-bus. The SYNC value could beused by timer circuits 30 to insure that reference values they receiveare stored in correct registers of the timer circuits. In still anotherembodiment, reference value identifiers (hereinafter RefIDs) may betransmitted concurrently with respective reference values to timercircuits 30 via bus 46 by a separate circuit under control of logiccontrol 64, and the RefIDs could be used by the timer circuits 30 toinsure that the reference values they receive are stored in the correctregisters. The remaining detailed description will presume that timercircuits 30 are sufficiently synchronized with reference-bus controller50 so that the SYNC value or the RefIDs are not needed by the timercircuits 30 to store reference values into the correct registers.

Event-Bus and Event-Bus Controller

Control system 10 of FIG. 1 further includes event-bus controller 38coupled to event-bus 34. With continuing reference to FIG. 1, FIG. 5illustrates relevant components of an example event-bus 34, it beingunderstood that the present invention should not be limited thereto. Asseen, event-bus 34 includes three sub-buses: event-signal bus 70,event-ID bus 72, and event-command bus 74. In an alternative embodiment,event-bus 34 may lack event-command bus 74.

In the example embodiment, timer circuits 30 may concurrently transmittheir event-IDs and corresponding event-signals to each other and to I/Ocircuits 32 via the event-signal bus 70 and event-ID bus 72,respectively. Likewise, ASC circuits 33 may concurrently transmit theirevent-IDs and corresponding event-signals to timer circuits 30 via theevent-signal bus 70 and event-ID bus 72, respectively. Timer circuits 30and ASC circuits 33, however, transmit their event-IDs and event-signalsonly when given permission by event-bus controller 38 in the exampleembodiment. As an aside, timer circuits 30 and/or ASC circuits 33 can beprogrammed to selectively ignore permission granted by event-buscontroller 38.

Timer circuits 30 may be assigned respective timer circuit identifiers,and ASC circuits 33 may be assigned respective ASC circuit identifiers.In one embodiment, each timer circuit 30 transmits its event-signal andcorresponding event-ID only when it receives permission in the form of asignal that contains the timer circuit identifier to which the timercircuit is assigned. Likewise each ASC circuit 33 transmits itsevent-signal and corresponding event-ID only when it receives permissionthat contains the ASC circuit identifier to which it is assigned.Event-command bus 74 or a separate bus (not shown) may transmit requestsfrom timer circuits 30 and ASC circuits 33 for permission to event-buscontroller 38. In the embodiment shown, all three buses 70-74 arecoupled to event-bus controller 38. In an alternative embodiment, onlyevent-command bus 74 is coupled to event controller 38. In thealternative that lacks an event-command bus, the event-ID bus 72 iscoupled to controller 38.

In one embodiment, event-bus controller 38 sends permission in a roundrobin fashion to timer circuits 30 and ASC circuits 33. Moreparticularly, event-bus controller 38 sends permission in sequentialorder to timer circuits 30, beginning with timer circuit 30-1 and endingwith ASC circuit 33-k. After permission is sent to ASC circuit 33-k,event-bus controller 38 repeats the process of sending permission insequential order, beginning again with timer circuit 30-1. This roundrobin process may be repeated until event-bus controller 38 receives astop command. Event-bus controller may skip any timer circuit 30 and ASCcircuit 33 that has not been programmed by CPU 40.

In one embodiment, each timer circuit 30 and ASC circuit 33 mayconcurrently transmit its event-signal and event-ID only when theevent-signal is in the ON state. However, the present invention will bedescribed with each timer circuit 30 concurrently transmitting itsevent-signal and event-ID for a short period of time (e.g., one cycle ofthe system clock mentioned above) in response to receiving permissionfrom event-bus controller 38, regardless of whether the event-signalstate is ON or OFF. Other embodiments are contemplated.

The present invention will be described with event-bus controller 38operating in the round robin manner described above, but the presentinvention should not be limited thereto. In an alternative embodiment,event-bus controller 38 can send permission to a timer circuit 30 or ASCcircuit 33 in response to event-bus controller 38 receiving a requestfor permission from that timer circuit 30 or ASC circuit 33 viaevent-command bus 74 or via a separate event-request bus (not shown).The request for permission should include the timer circuit identifieror ASC circuit identifier (mentioned above) of the timer circuit 30 orASC circuit 33 that is requesting the permission. In this embodiment,the timer circuit or ASC circuit may send a request when itsevent-signal transitions (i.e., changes from ON to OFF or from OFF toON). The conditions under which a timer circuit's or ASC circuit'sevent-signal transitions will be more fully described below.

When an event-request bus is employed, the event-request bus may becoupled to each timer circuit 30 and ASC circuit 33; however thisalternative embodiment can be extended to include two or moreevent-request buses (not shown). Each of these separate event-requestbuses would be coupled to a respective group of timer circuits 30 andASC circuits 33. For example a first event-request bus (not shown) maybe coupled between event-bus controller 38, timer circuits 30-1-30-12,and ASC circuits 33-1-33-3, while a second event-request bus (not shown)may be coupled between event-bus controller 38, timer circuits30-13-30-24, and ASC circuits 33-4-33-6, etc. With this arrangement,event-bus controller 38 may simultaneously receive separate requests forpermission from respective timer circuits or ASC circuits via respectiveevent-request buses. Assuming only one event-signal bus 70 and only oneevent-ID bus 72, event-bus controller 38 could prioritize the requestsand send permissions in accordance thereto via event-command bus 74 inorder to preclude collisions on the event-signal bus 70 and event-ID bus72.

In the embodiment in which event-bus 34 lacks a command bus 74, timercircuits 30 and ASC circuit 33 may send their event-signals in responseto receiving their assigned event-IDs from event-bus controller 38. Asnoted above, each timer circuit and ASC circuit is programmed with aunique event-ID, which may be known by event-bus controller 38. In thisembodiment, event-bus controller may send event-IDs to timer circuits 30and ASC circuits 33 via event-ID bus 72 in a round robin fashion or inresponse to receiving specific requests (that may contain event-IDs)from time circuits 30 and ASC circuits 33 via one or more of therequest-buses mentioned above. When a timer circuit 30 or ASC circuit 33receives an event-ID from controller 38 that matches the event-IDassigned to it, the timer circuit 30 will respond by outputting itsevent-signal onto bus 70. Timer circuit 30 or ASC circuit 33 could sendits event-signal while controller 38 is asserting the matching event-IDon the event-ID bus 72, or the timer circuit or ASC circuit could sendits event-signal immediately after controller 38 sends the matchingevent-ID but before controller 38 sends the next event-ID on bus 72.

I/O Circuits

With continuing reference to FIG. 1, I/O circuits 32 when programmed,generate control signals as a function of event-signals. With continuingreference to FIGS. 1 and 5, FIG. 6 illustrates in block diagram form,relevant components of an example I/O circuit 32-z. For purposes ofexplanation only, all I/O circuits 32 are assumed to include thecomponents shown in FIG. 6.

I/O circuit 32-z includes a compare circuit 76-z coupled to receiveevent-IDs from event-ID bus 72. Compare circuit 76-z is also coupledbetween programmable register 78-z and pass circuit 80-z. The output ofa pass circuit 80-z is provided to an S input of flip-flop 82-z and toan input of inverter 84-z. The output of inverter 84-z is coupled to anR input of SR flip-flop 82-z. Importantly, the control signals, such asthe spark signal mentioned above, are the Q output signals,respectively, of flip-flops 82.

Programmable register 78-z is coupled to communication path 42 (notshown in FIG. 6) and configured to receive and store an event-IDselected by CPU 40. Compare circuit 76-z continuously compares theevent-ID of register 78-z with event-IDs received from event-ID bus 72.In general, compare circuit 76-z generates a one-bit pass circuit signalin response to comparing the event-IDs. The pass circuit signal is ONwhen the event-ID of register 76-z equals the event-ID on bus 72.Otherwise, the pass circuit signal is OFF. In an alternative embodiment,each I/O circuit 32-z may include two or more programmable registers78-z coupled to compare circuit 76-z. Each of the separate event-IDregisters 76-z may store distinct event-IDs, and the pass circuit signalgenerated by compare circuit 76-z is ON if the event-ID received on bus72 equals any of the event-IDs stored in event-ID of registers 76-z.

In one embodiment, pass circuit 80-z may take form in a simpletransistor that couples event-signal bus 70 to the S input of flip-flop82-z and to the input of inverter 84-z when the pass circuit signal isON. When coupled, both the S input and inverter 84-z receive theevent-signal pending on event-signal bus 70. Initially, the Q output(i.e., control signal) of flip-flop 82-z is set to OFF, but will toggleto ON when the S input of flip-flop 82-z receives an event-signal thatis ON. While the control signal output of flip-flop 82-z is ON, it willtoggle to OFF when inverter 84-z receives an event-signal that is OFF. Acapacitor (not shown) could be added to hold the state of theevent-signal at the S input and the inventor 84-z input until theseinputs are coupled again to event-signal 70 via pass circuit 80.

As noted in the above example embodiment, event-signal bus 70 andevent-ID bus 72 operate in a round robin fashion; timer circuits 30 andASC circuits 33 transmit their event-signal/event-ID pairs, regardlessof event-signal state, in sequential fashion beginning with timercircuit 30-1 and ending with ASC circuit 33-k. One or more of the timercircuits 30 and ASC circuits 33 may be programmed, as will be more fullydescribed below, to transmit an event-ID that equals the event-IDprogrammed into, for example, register 78-1 of I/O circuit 32-1. Toillustrate, presume timer circuit 30-1 is configured to concurrentlytransmit event-ID=SPARK and event-signal ES-1, which is ON or OFF, whengiven permission by event-bus controller 38. Further, presume register78-1 of I/O circuit 32-1 stores SPARK as an event-ID. In this situation,when timer circuit 30-1 concurrently transmits event-signal ES-1 andSPARK to pass circuit 80-1 and compare circuit 76-1, respectively, passcircuit 80-1 will pass the event-signal ES-1 to flip-flop 82-1 andinverter 84-1 since compare circuit 76-1 detects a match between theSPARK event-ID on event-ID bus 72 and the SPARK event-ID in register78-1.

Timer circuits 30 and ASC circuits 33 will transmit their respectiveevent-signals for one system clock cycle at regularly scheduled times inaccordance with the example round robin process by which event-buscontroller 38 grants permission. As such, the minimum time period duringwhich flip-flop 82-z asserts the control signal (i.e., the Q output) inthe ON state, may be defined by (m+k)/(system clock frequency) where m+kis the total number of timer circuits 30 and ASC circuits 33. As anaside, (m+k)/(system clock frequency) presumes all timer circuits 30 andASC circuits 33 transmit their event-signals when given permission. Theminimum time period can be reduced if the system clock frequency isincreased, or if round-robin permission is given to only a subset of thetimer circuits 30 and ASC circuits 33. Presuming the frequency of thesystem clock is high enough, the minimum time period (m+k)/(system clockfrequency) of control signal assertion should have marginal effect tothe overall proper operation of the control system 10 and the enginecontrolled thereby.

The I/O circuit 32-z is described as a device that generates a controlsignal based on event-signals it receives from one or more of the timercircuits 30 and ASC circuits 33. However, as its name implies, the I/Ocircuit in another embodiment could also be used to receive anevent-signal for subsequent transmission to, for example, one or moretimer circuits 30 or other devices. The I/O circuit in this otherembodiment may need permission from event-bus controller 38 before itcan transmit the event-signal it receives in much the same manner thattimer circuits 30 and ASC circuits 33 need permission from event-buscontroller 38 before they send event-signal/event-ID pairs. However, thepresent invention will be described with I/O circuits 32 functioning asdevices that only generate control signals as described above.

Timer Circuits

Returning to FIG. 1, timer circuits 30 when programmed, generate one-bitevent-signals, which may be subsequently transmitted to each other andto I/O circuits 32 via event-bus 34. With continuing reference to FIGS.1 and 5, FIG. 7 illustrates relevant components of an example timercircuit 30-x, which includes a programmable memory device 86-x, areference match circuit 88-x, an event logic circuit 90-x, and inputexception (IE) circuits 92-x-0-92-x-3. For purposes of explanation only,it will be presumed that each of the timer circuits 30 shown in FIG. 1are identical in structure to timer circuit 30-x shown in FIG. 7. In analternative embodiment, one or more of the timer circuits 30 shown inFIG. 1 may have differences when compared to that shown in FIG. 7.

Programmable memory device 86-x, event logic circuit 90-x, and IEcircuits 92-x-0-92-x-3 are in data communication with CPU 40 viacommunication path 42 (not shown in FIG. 7). Programmable memory device86-x receives and stores lines of operational parameters from CPU 40.Each line of operational parameters may include a multibit referenceidentification (RefID), a multibit absolute match value (AMV), amultibit match condition (MC), a one-bit absolute or relative value(A/R), a one-bit single or continuous value (S/C), and four one-bitinput exception enablement (IEE(0)-IEE(3)) bits as shown.

Reference match circuit 88-x, event logic circuit 90-x, and/or IEcircuits 92-x-0-92-x-3 operate in accordance with the operationalparameters of programmable memory device 86-x or other operationalparameters provided by CPU 40. The present invention should not belimited to the operational parameters shown in the Figures or describedherein. Additional operational parameters may be employed to configureoperation of reference match circuit 88-x, event logic circuit 90-x,and/or IE circuits 92-x-0-92-x-3. For example, each line in programmablememory device 86-x may include a first operational parameter FOP (notshown). Reference match circuit 88-x may operate in one way when FOP isset to one value and when reference match circuit 88-x receives a firstcommand signal (more fully described below) from event logic circuit90-x, and reference match circuit 88-x may operate in a different waywhen FOP is set to another value and when reference match circuit 88-xreceives the first command signal from event logic circuit 90-x, allother conditions being equal. Further, each line may include a secondoperational parameter SOP (not shown), which is provided to event logiccircuit 90-x. SOP, depending on its value, may configure event logiccircuit 90-x to selectively ignore permission granted by event-buscontroller 38 to transmit timer circuit 30-x's event-signal ES-x andevent-ID. For example, event logic circuit 90-x can be configured totransmit its event-signal ES-x and/or event-ID onto event bus 34 onlyonce when ES-x first toggles from ON to OFF or from OFF to ON, eventhough event logic circuit 90-x is given subsequent permission totransmit its event-signal ES-x. Still further, event logic circuit 90-xmay store a maximum event count value (MECV) that is received from CPU40. As will be more fully described below, the event logic circuit 90 xcan compare MECV with a number of increment count IE commands that eventlogic circuit 90-x receives from one or more of IE circuits92-x-0-92-x-3. When the number increment count IE commands received fromone or more of the IE circuits 92-x-0-92-x-3 equals MECV, event logiccircuit 90-x will toggle its event-signal ES-x from OFF to ON or from ONto OFF, and event logic circuit 90-x will maintain the toggled state ofevent-signal ES-x event at least until event-logic circuit receives astart or restart IE command (more fully described below) from one of theIE circuits 92-x-0-92-x-3.

Programmable memory device 86-x shows four input exception enablementbits IEE(0)-IEE(3) corresponding to four IE circuits 92-x-0-92-x-3,respectively, it being understood that in alternative embodiments theprogrammable memory device may include more than four or less than fourinput exception enablement bits corresponding to respective IE circuits.

Each line of parameters in programmable memory device 86-x is addressedby a respective line number. As will be more fully described below,reference match circuit 88-x generates a line number value c, which isused by programmable memory device 86-x and event logic circuit 90-x.Reference match circuit 88-x changes the value of c during activeoperation. In response to receiving c, programmable memory device 86-xsends operational parameters of line c to reference match circuit 88-xand IE circuits 92-x. Thus, at any point in time reference match circuit88-x receives RefID-c, AMV-c, MC-c, A/R-c, and S/C-c, and IE circuits92-x-0-92-x-3 receive IEE(0)-c-IEE(3)-c, respectively. The value of cmay be affected by command signals that are received from event logiccircuit 90-x as will be more fully described below. Although not shown,programmable memory device 86-x may send one or more operationalparameters of line c to event logic circuit 90-x, and event logiccircuit 90-x may operate in accordance with the one or more operationalparameters it receives.

Reference match circuit 88-x generates a match-signal MS-x, the state ofwhich may depend on one or more of the reference values (e.g., Ts, FRAs,etc.) that are received from reference-bus controller 50 (see FIGS. 3and 4) via reference-bus 46. Event logic circuit 90-x, in turn, maygenerate its event-signal ES-x as a function of match-signal MS-x. Forthe purposes of explanation only, event-signal EX-x is presumed equal tomatch-signal MS-x, unless otherwise noted.

The state of event-signal ES-x may depend on an IE command from one ofIE circuits 92-x, as will be more fully described below. IE commands mayalso prompt event logic circuit 90-x to assert command signals (e.g.,start signal, reset signal, force signal, stop signal, etc, as will bemore fully described below), which may affect the state of match-signalMS-x, which in turn may affect the state of event-signal ES-x.

Event logic circuit 90-x includes a programmable register 98-x that isin data communication with CPU 40 via communication path 42 (not shownin FIG. 7). Programmable register 98-x stores an event-ID selected byCPU 40. Event logic circuit 90-x is coupled to receive permission fromevent-bus controller 38 via event-command bus 74 to transmit itsevent-signal and event-ID, and when given permission by event-buscontroller 38 (not shown in FIG. 7) event logic circuit 90-x, in theembodiment shown, concurrently transmits its event-signal ES-x,regardless of state, and event-ID of register 98-x onto event-signal bus70 and event-ID bus 72, respectively, for one cycle of the system clock.The present invention is described with reference to registers thattemporarily store event-IDs selected by CPU 40. In other words, theevent-IDs in these registers may be overwritten with new event-IDs. Inan alternative embodiment, one or more of these registers may beconfigured to permanently store event-IDs.

Each of the IE circuits 92-x contains a pair of programmable registers94-x-y and 96-x-y that are in data communication with CPU 40 via thecommunication path 42. Each programmable register 94-x-y is configuredto store one of many different IE codes selected by CPU 40. Eachprogrammable register 96-x-y is configured to store an event-ID selectedby CPU 40. IE circuits 92-x receive event-signals and event-IDs viaevent-signal bus 70 and event-ID bus 72, respectively. Additionally, IEcircuits 92-x receive respective input exception enablement IEE bitsfrom line c of programmable memory device 86-x. As noted, IE circuits92-x send IE commands to event logic circuit 90-x. When an IE circuit92-x-y receives an event-ID that matches the event-ID stored within itsprogrammable register 96-x-y and when its input exception enablement bitIEE(y)-c is ON, the IE circuit sends an IE command that corresponds tothe IE code that is stored within programmable register 94-x-y.

Reference Match Circuit

Event logic circuit 90-x may generate its event-signal ES-x as afunction of the match-signal MS-x generated by reference match circuit88-x, and the state of match-signal MS-x may depend on one or morereference values (e.g., FRAs, V1s, etc.). With continuing reference toFIG. 1, FIG. 8 illustrates the timer circuit 30-x of FIG. 7 with a moredetailed view of reference match circuit 88-x. As shown, reference matchcircuit 88-x includes a demultiplexer 100-x, which demultiplexesreference values (see FIGS. 3 and 4) it receives from reference-bus 46for subsequent capture by registers 102-x. A reference selection circuit104-x controls demultiplexer 100-x and registers 102-x to insure thatthe reference values are captured by the correct registers 102-x. Tothis end, reference selection circuit 104-x asserts a multibitdemultiplexer control signal, which is used by demultiplexer 100-x todemultiplex reference values Ts, FRAs, 720As, and V1s-V1ps to the inputsof registers 102-x-1-102-x-q, respectively, as the reference values aresequentially received from reference-bus 46. Selection circuit 104-xalso sequentially asserts one-bit control signals rs1-rsq forcontrolling registers 102-x-1-102-x-q, respectively. Registers102-x-1-102-x-q capture the reference values pending at their respectiveinputs in response to assertion of rs1-rsq, respectively. Referenceselection circuit 104-x is synchronized with reference-bus 46 so thatreference values Ts, FRAs, 720As, and V1s-V1ps are captured by registers102-x-1-102-x-q, respectively, as the reference values are received fromreference-bus 46. The process of capturing and storing reference valuesTs, FRAs, 720As, and V1s-V1ps into registers 102-x-1-102-x-q,respectively, is repeated with each new set of reference values that arereceived via reference-bus 46. Thus, the contents of registers 102-x areregularly updated with new reference values.

The outputs of registers 102-x are coupled to inputs of save registers106-x, respectively, and save registers 106-x capture the referencevalues of registers 102-x, respectively, in response to save registers106-x receiving a match pulse MP-x from arithmetic logic unit (ALU)114-x as will be more fully described below. The contents of saveregisters 106-x may be used to generate a relative match value RMV,which ALU circuit 114-x may compare with a regularly changing referencevalue of one of the registers 102-x as will be more fully describedbelow. The outputs of registers 102-x are coupled to respective inputsof multiplexer 110-x, and the outputs of save registers 106-x arecoupled to respective inputs of multiplexer 112-x as shown. Theoperational aspects of these multiplexers will be more fully describedbelow.

Reference match circuit 88-x and IE circuits 92-x operate according tooperational parameters contained in a selected line of programmablememory device 86. Programmable memory device 86-x receives line selectorvalue c from reference match circuit 88-x. In response, programmablememory device 86-x sends operational parameters in line c (e.g.,RefID-c, AMV-c, MC-c, etc.) to reference match circuit 88-x and IEcircuits 92-x. In essence, reference match circuit 88-x selects theoperational parameters it uses and used by IE circuits 92-x-0-92-x-3.

Reference match circuit 88-x includes a dynamic counter circuit 116-x,which generates the aforementioned line selector value c. In oneembodiment, dynamic counter circuit 116-x increments or decrements c inresponse to receiving a match pulse MP-x from ALU circuit 114-x. Dynamiccounter circuit 116-x also receives the S/C-c bit from programmablememory device 86-x. Dynamic counter circuit 116-x increments c by 1 whenS/C-c set to S for single, and dynamic counter circuit 116-x decrementsc by 1 when S/C-c is set to C for continuous.

Dynamic counter circuit 116-x resets c to 1 in response to receiving astart or stop signal from event logic circuit 90-x. With c set to 1,reference match circuit 88-x and IE circuits 92-x-0-92-x-3 receiveoperational parameters (e.g., RefID-1, AMV-1, MC-1, etc.) from line 1 ofprogrammable memory device 86-x. When dynamic counter circuit 116-xincrements c from 1 to 2, reference match circuit 88-x and IE circuits92-x-0-92-x-3 receive operational parameters (e.g., RefID-2, AMV-2,MC-2, etc.) from line 2 of programmable memory device 86-x. If dynamiccounter circuit 116-x decrements c from 2 back to 1 as it may if S/C-2is set to C for continuous, reference match circuit 88-x and IE circuits92-x-0-92-x-3 will again receive operational parameters from line 1 ofprogrammable memory device 86-x.

As noted above, dynamic counter circuit 116-x increments or decrements cin response to receiving a match pulse MP-x from ALU circuit 114-x,which operates in the active or inactive mode. In the active mode ALUcircuit 114-x can assert match pulses MP-x, and in the inactive mode ALUcircuit 114-x doesn't assert match pulses MP-x. ALU circuit 114-xoperates in the active mode until it receives a stop signal from eventlogic circuit 90-x, and ALU circuit 114-x will remain in the inactivestate until it receives a start signal from event logic circuit 90-x.

ALU circuit 114-x asserts a match pulse MP-x in response to receiving aforce signal (more fully described below) from event logic circuit 90-x.ALU circuit 114-x may also assert a match pulse MP-x in response tocomparing a reference value selected by multiplexer 110-x with eitherthe absolute match value AMV-c from programmable memory device 86-x or arelative match value RMV that is calculated by adder circuit 120-x. Forexample, ALU circuit 114-x may assert a match pulse MP-x when referencevalue V1s is found to compare equally with absolute match value AMV-1.

Outputs of multiplexers 110-x and 112-x are coupled to inputs of ALUcircuit 114-x and adder circuit 120-x, respectively, as shown.Multiplexers 110-x and 112-x select respective reference values storedin registers 102-x and 106-x, respectively, according to the referenceidentification RefID-c from line c of programmable memory device 86-x.To illustrate, when RefID-c is set to one of T, FRA, 720A, and V1-Vp,multiplexer 110-x selects a respective one of reference values Ts, FRAs,720As, and V1s Vps of registers 102-x, and in similar fashionmultiplexer 112-x selects a respective one of reference value Tm, FRAm,720Am, and V1m-Vqm of save registers 106-x. The reference value selectedby multiplexer 112-x is sent to adder circuit 120-x, which also receivesabsolute match value AMV-c from programmable memory device 86-x. Addercircuit 120-x, in turn, adds these two values to generate relative matchvalue RMV. Multiplexer 122-x selects either the RMV from adder circuit120-x or AMV-c from programmable memory device 86-x for input to ALUcircuit 114-x depending on the state of the absolute/relative bit A/R-c;if A/R-c is set to A for absolute, multiplexer 122-x selects AMV-c forinput to ALU circuit 114-x, and if A/R-c is set to R for relative,multiplexer 122-x selects RMV for input to ALU circuit 114-x.

In addition to receiving the reference value and either RMV or AMV-c,ALU circuit 114-x receives a match condition MC-c from programmablememory device 86-x. ALU circuit 114-x compares the reference value inputselected by multiplexer 110-x with either RMV or AMV-c to determine ifthe match condition MC-c is meet. For example, ALU circuit 114-x maycompare the input values to determine if they are equal to each other.If the inputs to ALU circuit 114-x satisfy the match condition MC-c, ALUcircuit 114-x asserts a short lived match pulse MP-x. For example, withMC-c set to “equal,” ALU circuit 114-x asserts the match pulse MP-x whenthe reference value selected by multiplexer 110-x equals either RMV orAMV-c, the value selected by multiplexer 122-x according to A/R-c.

MC-c may be encoded to define many different conditions such as: equalto, less than, greater than, less than or equal to, and greater than orequal to. In addition, MC-c may be set to “immediate.” As noted aboveALU circuit 114-x may assert the match pulse MP-x in response toreceiving a force match-signal from event logic circuit 90-x. With MC-cset to immediate, ALU circuit 114-x asserts a match pulse MP-x only whenALU circuit-x receives the force signal from event logic circuit 90-x.

As noted, the match pulse MP-x triggers save registers 106-x and dynamiccounter circuit 116-x; save registers 106-x capture the reference valuesin registers 102-x, respectively, in response to ALU circuit 114-xasserting the match pulse MP-x, and dynamic counter circuit 116-xincrements or decrements c in response to ALU circuit 114-x assertingthe match pulse MP-x. Save registers 106-x should capture the referencevalues in registers 102-x, respectively, before dynamic counter circuit116-x increments or decrements c. ALU circuit 114-x may be synchronizedwith reference selection circuit 104-x so that when ALU circuit 114-xasserts its match pulse MP-x, it is asserted immediately after thecontents of register 102-x-q are updated with a new reference value fromreference-bus 46 and before the contents of register 102-x-1 are updatedwith a new reference value from reference-bus 46.

Save registers 106-x and dynamic counter circuit 116-x are not the onlycomponents of timer circuit 30-x that receive the match pulse MP-x. Inaddition, SR flip-flop 124-x receives match pulse MP-x from ALU circuit114-x via demultiplexer 126-x, and SR flip flop 124-x toggles itsone-bit output Q in response thereto. Importantly, The Q output offlip-flop 124-x is the match-signal MS-x that is provided to and used byevent logic circuit 90-x for generating its event-signal ES-x. Thematch-signal MS-x also controls demultiplexer 126-x.

Timer circuit 30-x can be indirectly started or restarted by, forexample, another timer circuit 30 or event-bus controller 38 as will bemore fully described below. When started or restarted, event logiccircuit 90-x sends a start signal to ALU circuit 114-x and dynamiccounter circuit 116-x, which in turn activates ALU circuit 114-x andsets c to 1, if c is not already set to 1. In addition, event logiccircuit 90-x sends a reset signal to the R input of flip-flop 124-x,which sets the match-signal MS-x to OFF. When match condition MC-c ismeet as described above, or when event logic circuit 90-x asserts theforce signal, ALU circuit 114-x asserts and sends a match pulse MP-x tothe S or R input of flip-flop 124-x depending on the state of thematch-signal MS-x at the time; when the match-signal MS-x is ON, theoutput of ALU circuit 114-x is connected to the S input of flip-flop124, and when the match-signal MS-x is OFF, the output of ALU circuit114-x is connected to the R input of flip-flop 124-x. Match signal MS-xwill toggle from OFF to ON in response to ALU circuit 114-x assertingthe match pulse MP-x, and match-signal MS-x will remain in the ON stateuntil ALU circuit 114-x subsequently reasserts match pulse MP-x.

The foregoing describes several command signals issued by event logiccircuit 90-x, but additional command signals are contemplated. Forexample, event logic circuit 90-x could issue a capture signal thattriggers save registers 106-x to capture the reference values inregisters 102-x without ALU circuit 114-x generating a match pulse MP-x.Event logic circuit 90-x may issue several command signals in responseto receiving a IE command from one of the IE circuits 92-x. For example,event logic circuit could issue the capture signal along with a stopsignal that is transmitted to either ALU circuit 114-x or dynamiccounter circuit 116-x or both.

FIG. 9 illustrates relevant operational aspects of an example processperformed by reference match circuit 88-x in accordance with oneembodiment. The process initiates when event logic circuit 90-x assertsthe start signal mentioned above, which in turn activates ALU circuit116-x and resets c to 1. Event logic circuit 90-x also asserts the resetsignal, which in turn resets the match-signal MS-x to OFF. It is notedthat c should be set to 1 and match-signal MS-x should be set to OFFbefore event logic circuit 90-x asserts the start and reset signals. Forpurposes of explanation only, registers 102-x begin capturing respectivereference values as described above when event logic circuit 90-xasserts the start signal.

Event logic circuit 90-x can receive and store a value from programmablememory device 86-x or elsewhere, which represents the total number ofprogrammed lines therein. In step 134, event logic circuit 90-x comparesthe current value of c with the total number of programmed lines inprogrammable memory device 86-x. If c is greater than the total numberof programmed lines, the process ends by event logic circuit 90-xgenerating the stop signal, which in turn deactivates ALU circuit 116-xand resets c to 1. Event logic circuit 90-x also asserts the resetsignal, which in turn resets the match-signal MS-x to OFF.

Presuming c is less than or equal to the total number of lines inprogrammable memory device 86-x, programmable memory device 86-x sendsoperational parameters of line c to reference match circuit 88-x and IEcircuits 92-x. For example, the selector input of multiplexers 110 and112 receive reference identifier RefID-c, ALU circuit 114 receives MC-c,dynamic counter circuit 116 receives S/C-c, adder circuit 120 receivesAMV-c, and multiplexer 122 receives AMV-c and A/R-c. Before the processof FIG. 9 is started, c is initially set to 1, so step 136 may beskipped initially. For purposes of explanation only, S/C-1 ofprogrammable memory device 86 is always set to S for single and A/R-1 isalways set to A for absolute in each programmed timer circuit 30.

At step 138, multiplexer 112-x selects a reference value stored in oneof the save registers 106 that corresponds to RefID-c. The referencevalue selected in step 138 is added to AMV-c by adder circuit 120-x instep 140 to generate RMV, which is subsequently provided to multiplexer122-x. In step 142, multiplexer 122-x selects one of the two inputvalues thereto (i.e., the absolute match value AMV-c or the relativematch value RMV generated by adder circuit 120-x) in accordance with theabsolute/relative bit A/R-c. As an aside, when c is set to 1, step 138and step 140 are irrelevant since A/R-1 is presumed set to A, and as aresult ALU circuit 114-x initially compares the reference value selectedby multiplexer 110-x with absolute match value AMV-1 to determinewhether match condition MC-1 is met.

The value selected in step 142 is provided as one input of ALU circuit114-x. Multiplexer 110-x selects the other input to ALU circuit 114-x.Specifically, in step 144, multiplexer 110-x selects one of thereference values of registers 102-x that corresponds to RefID-c. In step146, ALU circuit 114-x compares the two inputs in order to determinewhether the match condition MC-c is met.

The match condition MC-c can be any one of many different matchconditions, including: equal to, equal to or less than, immediate, etc.To illustrate, with match condition MC-c set to “equal to or greaterthan,” the match condition MC-c will be met if the reference valueselected by multiplexer 110-x is equal to or greater than the valueselected by multiplexer 122-x. If the match condition MC-c is not met,the process returns to step 144. Because the contents of registers 106-xare regularly updated, a new reference value may be selected in step 144for subsequent comparison in step 146.

When the match condition MC-c is met in step 150, ALU circuit 114-x willassert a match pulse MP-x, which is subsequently demultiplexed to eitherthe S input or the R input of flip-flop 124-x, which in turn toggles thematch state MS-x signal as shown in step 152. Also, the reference valuesheld in save registers 106-x are overwritten with the reference valuesheld in registers 102-x, respectively, as shown in step 154. Thereafter,dynamic counter 116-x either increments or decrements the c, dependingon the value of S/C-c, and the process returns to step 134 and continuestherefrom if c does not exceed the total number of lines of operationalparameters. As an aside, if S/C-c is set to C for continuous, referencematch circuit 88-x will enter a loop state during which it willalternate between operation in accordance with the operationalparameters of line c and operation in accordance with the operationalparameters of line c-1.

With continuing reference to FIG. 8, FIGS. 10A and 10B show exampletiming diagrams of the match-signal MS-x that are generated by referencematch circuit 88-x in accordance with the process shown in FIG. 9. InFIG. 10A, programmable memory device 86-x includes 2 lines of exampleoperational parameters. With c previously set to 1, the operationalparameters of line 1 are provided to various components of timer circuit30-x, including reference match circuit 88-x and IE circuits 92-x.Because match-signal MS-x is initially reset to OFF, the first matchpulse MP-x generated by ALU circuit 114-x will be transmitted to the Sinput of flip-flop 124-x via demultiplexer 126-x. The A/R-1 bit in line1 of programmable memory device 86-x in FIG. 10A is set to A orabsolute, which means that multiplexer 122-x selects absolute matchvalue AMV-1=500 as one input for ALU circuit 114-x. Line 1 indicatesthat RefID-1=720A (the 720 angle reference value), which meansmultiplexer 110-x selects reference value 720As of register 102-x-3 asthe other input to ALU circuit 114-x in accordance with step 144.Because MC-1 is set to “equal,” ALU circuit 114-x will assert a matchpulse MP-x when the inputs to ALU circuit 114-x are equal. Presuming ALUcircuit 114-x receives 720As=500 at time t1, ALU circuit 114-x willassert match pulse MP-x, which toggles match-signal MS-x to ON inaccordance with step 152. Shortly after time t1, the save registers106-x capture the reference values of registers 102-x, respectively, inaccordance with step 154. Dynamic counter 110-x increments c from 1 to 2since S/C-1=S in accordance with step 156, and the process branches tostep 134 to test the c value.

Because c is less than or equal to 2, the total number of lines ofoperational parameters in the illustrated example, the process proceedsto step 136. With c=2 the operational parameters of line 2 shown in FIG.10A are sent to various components of the timer circuit 30-x. BecauseRefID-2=T (the time domain reference), multiplexer 112-x sends thereference value Tm stored in save register 106-x-1 to adder circuit120-x, which in turn adds reference value Tm to AMV-2=10, thusgenerating the relative match value RMV=Tm+10 in accordance with step140. With RefID-2=T as shown, multiplexer 110-x selects the referencevalue Ts of register 102-x-1 as one input to ALU circuit 114-x.Multiplexer 122-x selects RMV=Tm+10 as the other input to ALU circuit114-x since A/R-2 is set to R for relative. Line 2 includes matchcondition MC-2 set to “greater than or equal to,” and as a result ALUcircuit 114-x will assert a match pulse MP-x when Ts is greater than orequal to RMV=Tm+10. Presuming ALU circuit 114-x receives reference valueTs=RMV=Tm+10 at time t2, ALU circuit 114-x asserts a second match pulseMP-x, which in turn is transmitted to the R input of flip-flop 124-x viademultiplexer 126-x since the match-signal MS-x is set to ON. As aresult, the match-signal MS-x toggles to OFF at time t2 in accordancewith step 152, and save registers 106-x capture the reference values ofregisters 102-x, respectively, in accordance with step 154. Dynamiccounter 110-x increments c to 3 since S/C-2=S in accordance with step156, and the process branches to step 134 to test the c value. Because cis greater than 2, the example process ends.

In the second example of FIG. 10B, programmable memory device 86includes 4 lines of operational parameters. With c previously set to 1,the operational parameters of line 1 are provided to various componentsof timer circuit 30-x, including reference match circuit 88-x and IEcircuits 92-x. Because match-signal MS-x is initially reset to OFF, thefirst match pulse MP-x asserted by ALU circuit 114-x will be transmittedto the S input of flip-flop 124-x via demultiplexer 126-x. The A/R-1 bitof line 1 is set to A for absolute in FIG. 10B, which means thatmultiplexer 122-x selects absolute match value AMV-1=20 as one input forALU circuit 114-x. RefID-1=720A, which means multiplexer 110-x initiallyselects the reference value 720As of register 102-x-3 as the secondinput to ALU circuit 114-x in accordance with step 144. Because MC-1 isset to “equal,” ALU circuit 114 will assert a match pulse MP-x when theinputs to ALU circuit 114-x are equal. Presuming ALU circuit 114-xreceives 720As=20 at time t1, ALU circuit 114-x will assert the matchpulse MP-x, which toggles match-signal MS-x to ON in accordance withstep 152. Shortly after time t1, the save registers 106-x capture thereference values of registers 102-x, respectively, in accordance withstep 154. Dynamic counter 110-x then increments c from 1 to 2 sinceS/C-1=S in accordance with step 156, and the process branches to step134 to test the c value.

Because c is less than or equal to 4, the total number of lines ofoperational parameters in the example, the process proceeds to step 136.With c=2 the operational parameters of line 2 shown in FIG. 10B areprovided to various components of timer circuit 30-x, includingreference match circuit 88-x and IE circuits 92-x. Because RefID-2=FRA(the free running angle reference value), multiplexer 112-x sends thereference value FRAm stored in register 106-x-2 to adder circuit 120-x,which in turn adds reference value FRAm to AMV-2=25, thus generating therelative match value RMV=FRAm+25 in accordance with step 140. WithRefID-2=FRA as shown, multiplexer-x 110 selects the reference value FRAsof register 102-x-2 as one input to ALU circuit 114-x. Multiplexer 122-xselects RMV=FRAm+25 as the second input to ALU circuit 114-x since A/R-2is set to R for relative. Line 2 includes match condition MC-2 set to“equal,” and as a result ALU circuit 114-x will assert a match pulseMP-x when FRAs is equal to RMV=FRAm+25. Presuming ALU circuit 114-xreceives FRAs=RMV=FRAm+25 at time t2, ALU circuit 114-x asserts a secondmatch pulse MP-x, which in turn is transmitted to the R input offlip-flop 124-x via demultiplexer 126-x. As a result, the match-signalMS-x toggles to OFF at time t2 in accordance with step 152, and saveregisters 106-x capture the reference values of registers 102-x,respectively, in accordance with step 154. Dynamic counter 110-xincrements c to 3 since S/C-2=S in accordance with step 156, and theprocess branches to step 134 to test the c value.

Because c is less than or equal to 4, the process proceeds to step 136.With c=3 the operational parameters of line 3 shown in FIG. 10B areprovided to various components of timer circuit 30-x. Because RefID-3=T,multiplexer 112-x sends the reference value Tm stored in register106-x-1 to adder circuit 120-x, which in turn adds reference value Tm toAMV-3=20, thus generating the relative match value RMV=Tm+20 inaccordance with step 140. With RefID-3=T as shown, multiplexer 110-xselects the reference value Ts of register 102-x-1 as one input to ALUcircuit 114-x. Multiplexer 122-x selects RMV=Tm+20 as the other input toALU circuit 114-x since A/R-3 is set to R for relative. Line 3 includesmatch condition MC-3 set to “greater than or equal to,” and as a resultALU circuit 114-x will assert a match pulse MP-x when Ts is greater thanor equal to RMV=Tm+20. Presuming ALU circuit 114-x receives Ts=RMV=Tm+20at time t3, ALU circuit 114-x asserts a third match pulse MP-x, which inturn is transmitted to the S input of flip-flop 124-x via demultiplexer126-x. As a result, the match-signal MS-x toggles to ON at time t3 inaccordance with step 152, and save registers 106-x capture the referencevalues of registers 102-x, respectively, in accordance with step 154.Dynamic counter 110-x increments c to 4 since S/C-3=S in accordance withstep 156, and the process branches to step 134 to test the c value.

Because c is now equal than 4, the process proceeds to step 136. Withc=4 the operational parameters of line 4 shown in FIG. 10B are sent tovarious components of timer circuit 30-x. Because RefID-4=V1 (thequantity of current flowing to coil 16 of FIG. 1), multiplexer 112-xsends the reference value V1m stored in register 106-x-4 to addercircuit 120-x, which in turn adds reference value V1m to AMV-4=10, thusgenerating the relative match value RMV=V1m+10 in accordance with step140. With RefID-4=V1 as shown, multiplexer 110-x selects the referencevalue V1s of register 102-x-4 as one input to ALU circuit 114-x.Multiplexer 122-x selects AMV-4=10 as the other input to ALU circuit114-x since A/R-4 is set to A. Line 4 includes match condition MC-4 setto “equal,” and as a result ALU circuit 114-x will assert a match pulseMP-x when V1s is equal to AMV-4=10. Presuming ALU circuit 114-x receivesV1s=AMV-4=10 at time t4, ALU circuit 114-x asserts a fourth match pulseMP-x, which in turn is transmitted to the R input of flip-flop 124-x viademultiplexer 126-x. As a result, the match-signal MS-x toggles to OFFat time t4 in accordance with step 152, and save registers 106-x capturethe reference values of registers 102-x, respectively, in accordancewith step 154. Dynamic counter 110 then decrements c to 3 since S/C-4=Cin accordance with step 156.

Because S/C-4 is set to C for continuous, line selector value c willalternate between 3 and 4 and reference match circuit 88-x will enter aloop state. From time t4 on, the timing diagram of FIG. 10B shows MS-xrepeatedly toggling in accordance with the operational parameters ofalternating lines 3 and 4. When c first decrements to 3, the operationalparameters of line 3 are resent to various components of timer circuit30, including reference match circuit 88-x and IE circuits 92-x, inaccordance with step 136. Presuming ALU circuit 114-x receivesTs=RMV=Tm+20 at time t5, ALU circuit 114-x asserts a fifth match pulseMP-x, just as it asserted the third match pulse MP-x at time t3. Thefifth match pulse MP-x is transmitted to the S input of flip-flop 124-xvia demultiplexer 126. As a result, the match-signal MS-x toggles to ONat time t5 in accordance with step 152, and save registers 106-x capturethe reference values of registers 102-x, respectively, in accordancewith step 154. Dynamic counter 110-x increments c to 4 since S/C-3=S inaccordance with step 156, and the process proceeds as described in theimmediately preceding paragraph, which eventually results withmatch-signal MS-x toggling to OFF at time t6 just as it did at time t4.Reference match circuit 88-x may continue in the loop state until itreceives a stop signal from event logic circuit 90-x. It is noted thatthe time difference between t2 and t3 is the same as the time differencebetween t4 and t5 and the time difference between time t6 and time t7.However, the time difference between times t5 and t6 is less than thetime difference between time t3 and t4. Because of the particularoperational parameters shown in FIG. 10B, the length of time between t7and t8 is greater than the length of time between times t5 and t6.

IE Circuits

Returning to FIG. 8, when given permission event logic circuit 90-xtransmits its event-signal ES-x to other timing circuits 30 and I/Ocircuits 32 via event-signal bus 70. In general event logic circuit 90-xgenerates its event-signal ES-x as a function of the match-signal MS-xit receives from reference match circuit 88-x. Normally, theevent-signal ES-x is equal to the match-signal MS-x. The state of thematch-signal MS-x and/or the event-signal ES-x are sensitive to IEcommands that event logic circuit 90-x receives from IE circuits 92-x aswill be more fully described below.

With continuing reference to FIG. 8, FIG. 11 illustrates in blockdiagram form, relevant components of an example IE circuit 92-x-y. TheIE circuit 92-x-y includes an IE command logic 160-x-y coupled toreceive input exception enablement bit IEE(y)-c from programmable memorydevice 86-x, a Q output of flip-flop 172-x-y, and an IE code fromprogrammable register 94-x-y. IE circuit 92-x-y is configured to sendone of many different types of IE commands to event logic circuit 90-x(not shown in FIG. 11) as will be more fully described below. Each ofthese IE commands, when received by event logic circuit 90-x may affectoperation of the timer circuit 30 in general and event-signal ES-x inparticular. It is noted that two or more of the IE circuits 92-x shownin FIG. 8 may receive and store different IE codes in their respectiveIE code registers 94-x. In another embodiment, two of the IE circuitsmay contain the same IE codes in their IE code registers 94-x.

IE code register 94-x-y receives and stores a multibit code IE code thatwas previously selected by CPU 40. In general, IE circuit 92-x-y sendsor asserts an IE command corresponding to the IE code in register 94-x-ywhen both the input exception enablement bit IEE(y)-c and the Q outputof flip-flop 162-x-y are ON. In one embodiment, IE command logic 160-x-ymay include a memory device (not shown) that stores a table, which mapsIE codes to respective IE commands. Table 1 below illustrates a mappingbetween example IE codes and their respective IE commands.

TABLE 1 IE Code IE Command ST-H Start on Assertion RST-H Restart onAssertion STOP-H Stop on Assertion F-H Force on Assertion F-OFF-L ForceOFF on Termination MASK Mask SPD Suspend PP Postpone IC IncrementCounter

When the table (or the memory device that stores the table) receives anIE code from register 94-2-y, the table outputs an IE command that ismapped to the IE code, and IE command logic 160-x-y sends this mapped IEcommand to event logic circuit 90-x when both the input exceptionenablement bit IEE(y)-c and the Q output of flip-flop 162-x-y are ON.Other embodiments of IE command logic 160-x-y are contemplated.

IE circuit 92-x-y further includes event-ID register 96-x-y thatreceives and stores an event-ID selected by CPU 40. The event-ID ofevent-ID register 96-x-y is continuously compared by compare circuit170-x-y to the event-IDs received on event-ID bus 72. When comparecircuit 170-x-y detects a match, compare circuit 170-x-y asserts a passsignal which is provided to pass circuit 172-x-y. In one embodiment,pass circuit 172-x-y may take form in a simple transistor, the gate ofwhich is coupled to the output of compare circuit 170-x-y. Regardless ofthe form, pass circuit 172-x-y passes the event-signal on event-signalbus 70 to the S input of flip-flop 162-x-y and to the input of inverter174-x-y while the pass signal is asserted ON. A capacitor (not shown)could be added to hold the state of the event-signal at the S input andthe input of inventor 174-x-y until these inputs are again coupled toevent-signal bus 70 via pass circuit 172-x-y.

The event-bus, including the event-signal bus 70 and the event-ID bus72, operate in a round robin fashion; timer circuits 30 transmit theirevent-signal/event-ID, regardless of event-signal state, in sequentialfashion beginning with timer circuit 30-1 and ending with timer circuit30-m. One or more of the timer circuits 30 may be programmed, as will bemore fully described below, to transmit an event-ID that equals theevent-ID programmed into, for example, register 96-1-1 of IE circuit92-1-1. To illustrate, presume timer circuit 30-2 is configured totransmit event-ID=DDA, along with its event-signal ES-2, when givenpermission by event-bus controller 38. Further, presume register 96-1-1of IE circuit 92-1-1 stores event-ID=DDA. When timer circuit 30-2concurrently transmits ES-2 and DDA to pass circuit 172-1-1 and comparecircuit 170-1-1, respectively, pass circuit 172-1-1 passes event-signalES-2 since compare circuit 172-1-1 finds a match between the DDAevent-ID it receives and the DDA event-ID in register 96-1-1.

Timer circuits 30 will transmit their respective event-signals for onesystem clock cycle at regularly scheduled times in accordance with theround robin process by which event-bus controller 38 grants permission.Like the flip-flops of the I/O circuits 32, the minimum time periodduring which flip-flop 162-x-y asserts the Q output in the ON state, isdefined by m/(system clock frequency) where m is the total number oftimer circuits 30. The minimum time period can be reduced if the systemclock frequency is increased.

Event Logic Circuit

As noted, IE command logic 160-x-y sends or asserts an IE commandcorresponding to the IE code in register 94-x-y only when both theexception enablement bit IEE(y)-c of programmable memory device 86-x andthe Q output of flip-flop 162-x-y are ON. At any point in time, eventlogic circuit 90-x may receive one or more IE commands from IE circuits92-x.

Event logic circuit 90-x may take form in hardware, software or acombination of hardware and software. In one embodiment event logiccircuit 90-x may include a processor that processes received IE commandsin accordance with executable instructions stored in memory (not shown).In another embodiment, event logic circuit 90-x may take form in a fieldprogrammable gate array. In a preferred embodiment, event logic circuit90-x lacks a processor and instructions executable by the processor;rather event logic circuit 90 is a fast, hardwired circuit thatincludes, for example, interconnected logic gates, registers,flip-flops, etc.

Event logic circuit 90-x responds differently to different IE commandsfrom IE circuits 92-x. With continuing reference to FIGS. 8, 9, and 11,FIGS. 12A-12F illustrate timing diagrams that show relevant aspects ofevent logic circuit 90-x's operation in response to assertion of exampleIE commands.

Start IE Command

In general, when event logic circuit 90-x receives a start IE command,or any variation thereof, event logic circuit 90-x may send a startsignal to ALU circuit 114-x and dynamic counter circuit 116-x, which inturn activates ALU circuit 114-x and sets c to 1. In addition eventlogic circuit 90-x may send a reset signal to flip-flop 124-x, whichresets match-signal MS-x to OFF. Thereafter, the reference match circuit88-x may begin operating in accordance with the process shown in FIG. 9.

The present invention contemplates multiple variations of the start IEcommand. For example, in response to receiving a “start-on-assertion” IEcommand, event logic circuit 90-x will immediately send the start andreset signals when one of the IE circuits 92-x first asserts thestart-on-assertion IE command. In response to receiving a“start-on-assertion-OFF” IE command, event logic circuit 90-x will sendthe start and reset signals only if event-signal ES-x is in the OFFstate when the IE circuit 92-x first asserts the start-on-assertion-OFFIE command.

FIG. 12A illustrate timing diagrams that show relevant aspects of eventlogic circuit 90-x and reference match circuit 88-x's operation inresponse to assertion of a start-on-assertion IE command. For purposesof explanation, it will be presumed that IE circuit 92-x-0 is programmedto assert the start-on-assertion IE command. FIG. 12A illustrates timingdiagrams for: the match-signal MS-x generated by reference match circuit88-x, the event-signal ES-x generated by event logic circuit 90-x, andthe assertion of the start-on-assertion IE command by IE circuit 92-x-0.FIG. 12A also shows example operational parameters, including exceptionenablement bits IEE(0)-IEE(3), of memory device 86-x. It is noted thetiming diagrams of FIGS. 12A-12F do not show the IE commands, ratherthey show the time periods when the IE commands are asserted.

In general, none of the IE circuits 92-x-0-92-x-3 can assert an IEcommand unless its input exception enablement bit is ON. As shown inFIG. 12A, the input exception enablement bits are set to 0=OFF exceptfor IEE(0)-1=1=ON. With c equal to 1, IE circuit 92-x-0 is enabled toassert the start-on-assertion IE command since IEE(0)-1 is set to 1=ON.However, IE circuit 92-x-0 will not be enabled to assert thestart-on-assertion IE command after c is incremented to 2 since IEE(0)-2is set to 0=OFF.

At times t1 and t5, IE circuit 92-x-0 receives an event-signal that isON along with an event-ID that matches the event-ID in register 96-x-0,and as a result IE circuit 92-x-0 asserts the start-on-assertion IEcommand as shown. At times t2 and t6, IE circuit 92-x-0 receives anevent-signal that is OFF along with event-ID that matches the event-IDin register 96-x-0, and as a result IE circuit 92-x-0 terminates theassertion of the start-on-assertion IE command as shown.

Event logic circuit 90-x responds to a start-on-assertion IE command bysending a start signal to ALU circuit 114-x and dynamic counter circuit116-x, and by sending a reset signal to flip-flop 124-x. Thereafterreference match circuit 88-x begins to operate in accordance with theprocess shown in FIG. 9. During the course of operation, reference matchcircuit 88-x generates the match-signal MS-x shown in FIG. 12A. Thetiming diagrams of FIG. 12A were drawn with the presumption that thevalue of 720As is greater than or equal to AMV-1=300 at time t3, andthat the value of Ts is greater than or equal to RMV=Tm+20 at time t4.As such, reference match circuit 88-x asserts the match-signal MS-xbetween t3 and t4, and because the event-signal ES-x is presumed equalto the match-signal MS, event logic circuit 90 asserts the event-signalES-x at the same time. A reassertion of the start-on-assertion IEcommand, or any variation thereof, will have no effect, regardless ofthe input exception enablement bits IEE(0)-IEE(3), unless event logiccircuit 90 receives a variation of the stop IE command in theintervening period between successive start-on-assertion IE commands.Again, event logic circuit 90-x responds at time t1, the time when thestart-on-assertion IE command is first asserted.

Restart IE Command

In general, when event logic circuit 90-x receives a restart IE command,or any variation thereof, event logic circuit 90-x sends a start signalto ALU circuit 114-x and dynamic counter circuit 116-x, which in turnactivates ALU circuit 114-x and sets c to 1. In addition event logiccircuit 90-x sends a reset signal to flip-flop 124-x, which resetsmatch-signal MS-x to OFF. Thereafter, the reference match circuit 88-xmay begin operating in accordance with the process shown in FIG. 9.

The present invention contemplates multiple variations of the restart IEcommand. For example, in response to receiving a “restart-on-assertion”IE command, event logic circuit 90-x will immediately send the start andreset signals when one of the IE circuits 92-x first asserts therestart-on-assertion IE command. In response to receiving a“restart-on-termination-OFF” IE command, event logic circuit 90-x willsend the start and reset signals only if event-signal ES-x is in the OFFstate when IE circuit 92-x-y terminates the assertion of therestart-on-termination-OFF IE command.

FIG. 12B illustrate timing diagrams that show relevant aspects of eventlogic circuit 90-x and reference match circuit 88-x's operation inresponse to the assertion of a restart-on-assertion IE command. Thestart-on-assertion and restart-on-assertion IE commands result insimilar effects; however, unlike the start-on-assertion IE command,event logic circuit 90-x reacts to successive assertions of therestart-on-assertion IE command by resending the start and reset signalsto match circuit 88-x.

For purposes of explanation, it will be presumed that IE circuit 92-x-0is programmed to assert the restart-on-assertion IE command. FIG. 12Billustrates timing diagrams for: the match-signal MS-x generated byreference match circuit 88-x, the event-signal ES-x generated by eventlogic circuit 90-x, and the assertion of the restart-on-assertion IEcommand by IE circuit 92-x-0. FIG. 12B also shows example operationalparameters of programmable memory device 86-x, including exceptionenablement bits IEE(0)-IEE(3).

As shown in FIG. 12B, the input exception enablement bits are set to0=OFF except for IEE(0)-1 and IEE(0)-2. With c equal to either 1 or 2,IE circuit 92-x-0 is enabled to assert the restart-on-assertion IEcommand. At times t1, t5, and t8, IE circuit 92-x-0 receives anevent-signal set to ON along with an event-ID that matches the event-IDin register 96-x-0, and as a result IE circuit 92-x-0 asserts therestart-on-assertion IE command as shown. At times t2, t6, and t9,compare circuit 170-x-0 receives an event-signal set to OFF along withan event-ID that matches the event-ID in register 96-x-0, and as aresult, IE circuit 92-x-0 terminates the assertion of therestart-on-assertion IE command as shown.

Event logic circuit 90-x-0 responds to assertion of therestart-on-assertion IE command by sending a start signal to ALU circuit114-x and dynamic counter circuit 116-x in addition to sending a resetsignal to flip-flop 124-x. Thereafter reference match circuit 88-xbegins to operate in accordance with the process shown in FIG. 9. Duringthe course of operation, reference match circuit 88-x generates thematch-signal MS-x shown in FIG. 12B. The timing diagrams of FIG. 12Bwere drawn with the presumption that the value of 720As is greater thanor equal to AMV-1=300 at time t3, and that the value of Ts is greaterthan or equal to RMV=Tm+20 at time t4. As such, reference match circuit88-x asserts the match-signal MS-x between t3 and t4, and withevent-signal ES-x presumed equal to the match-signal MS-x, event logiccircuit 90-x-0 asserts the event-signal ES-x at the same time.

When IE circuit 92-x-0 reasserts the restart-on-assertion IE command attimes t5 and t8, event logic circuit 90 resends the start signal to ALUcircuit 114-x and dynamic counter circuit 116-x in addition to sendingthe reset signal to flip-flop 124-x. Thereafter match circuit 88-xrestarts operation in accordance with the process shown in FIG. 9 atthose times. The timing diagrams of FIG. 12B were drawn with thepresumption that reference value 720As is greater than or equal to 300at times t7 and t10, and that reference value Ts selected in step 144 isgreater than or equal to Tm+20 at time t11. It is noted that IE circuit92-x-0 asserts the restart-on-assertion IE command and event logiccircuit 90-x resends the start and reset signals before reference matchcircuit 88-x completes the process it started at time t8, and as aresult, both the match-signal MS-x and the event-signal ES-x toggle OFF.

Stop IE Command

For purposes of explanation only, all programmed timer circuits 30 willhave at least one IE circuit 92-x-y that is programmed to assert thestart-on-assertion or restart-on-assertion IE command. However, morethan one of the IE circuits 92-x can be concurrently programmed by CPU40 and enabled by input exception bits. For example, a timer circuit30-x could have separate IE circuits 92-x that are programmed to assertthe start-on-assertion IE command and a variation of the stop IEcommand. In general, when event logic circuit 90-x receives anyvariation of a stop IE command, event logic circuit 90-x sends a stopsignal to ALU circuit 114-x and dynamic counter circuit 116-x, which inturn deactivates ALU circuit 114-x and sets c to 1. In addition eventlogic circuit 90-x sends a reset signal to flip-flop 124-x, which resetsmatch-signal MS-x, and thus ES-x, to OFF.

The present invention contemplates multiple variations of the stop IEcommand. For example, in response to receiving a “stop-on-assertion” IEcommand, event logic circuit 90-x will immediately send the stop andreset signals when one of the IE circuits 92-x first asserts thestop-on-assertion IE command. In response to receiving a“stop-on-assertion-ON” IE command, event logic circuit 90-x will sendthe stop and reset signals only if event-signal ES-x is ON when IEcircuit 92-x-y first asserts the stop-on-assertion-ON IE command.

FIG. 12C illustrate timing diagrams that show relevant aspects ofreference match circuit 88-x and event logic circuit 90-x's operation inresponse to the assertion of a start-on-assertion IE and astop-on-assertion IE command. For purposes of explanation, it will bepresumed that IE circuit 92-x-0 and 92-x-1 are programmed to assert thestart-on-assertion and stop-on-assertion IE commands, respectively.

FIG. 12C illustrates timing diagrams for: the match-signal MS-xgenerated by reference match circuit 88-x, the event-signal ES-xgenerated by event logic circuit 90-x, the assertion of thestart-on-assertion IE command by IE circuit 92-x-0, and the assertion ofthe stop-on-assertion IE command by IE circuit 92-x-1. FIG. 12C alsoshows example operational parameters of programmable memory device 86-x,including exception enablement bits IEE(0)-IEE(3).

As shown in FIG. 12C, the input exception enablement bits are set to0=OFF except for IEE(0)-1, IEE(1)-1, IEE(0)-2 and IEE(1)-2. With c isequal to either 1 or 2, IE circuit 92-x-0 is enabled to assert thestart-on-assertion IE command, and IE circuit 92-x-1 is enabled toassert the stop-on-assertion IE command. At time t1 IE circuit 92-x-0simultaneously receives an event-signal set to ON and an event-ID thatmatches the event-ID in register 96-x-0, and as a result, IE circuit92-x-0 asserts the start-on-assertion IE command as shown. At times t2,IE circuit 92-x-0 receives an event-signal set to OFF and event-ID thatmatches the event-ID in register 96-x-0, and as a result, IE circuit92-x-0 terminates the assertion of the start-on-assertion IE command. Attime t5 IE circuit 92-x-1 receives an event-signal set to ON and anevent-ID that matches the event-ID in register 96-x-1, and as a result,IE circuit 92-x-1 asserts the stop-on-assertion IE command as shown. Attime t7, IE circuit 92-x-1 receives an event-signal set to OFF and anevent-ID that matches the event-ID in register 96-x-1, and as a result,IE circuit 92-x-1 terminates the assertion of the stop-on-assertion IEcommand as shown.

Event logic circuit 90-x-0 responds to the start-on-assertion IE commandby sending a start signal to ALU circuit 114-x and dynamic countercircuit 116-x, and by sending a reset signal to flip-flop 124-x.Thereafter reference match circuit 88-x begins to operate in accordancewith the process shown in FIG. 9. During the course of operation,reference match circuit 88-x generates the match-signal MS-x shown inFIG. 12C. The timing diagrams of FIG. 12C were drawn with thepresumption that reference value 720As is greater than 300 at time t3,and that reference value Ts selected in step 144 is greater than Tm+20at time t4. As such, reference match circuit 88-x asserts thematch-signal MS-x between t3 and t4 as shown, and because theevent-signal ES-x is presumed equal to the match-signal MS-x, eventlogic circuit 90-x-0 asserts the event-signal ES-x at the same time.

The S/C-2 bit in programmable memory device 86-x is set to C forcontinuous, which means reference match circuit 88-x will enter a loopstate in accordance with the process of FIG. 9 as described above. Thetiming diagrams of FIG. 12C were drawn with the presumption thatreference value 720As is greater than 300 at time t5, and as a resultreference match circuit 88-x toggles the match-signal MS-x from OFF toON as shown. However, at time t6 IE circuit 92 asserts thestop-on-assertion IE command, and event logic circuit 90-x in turn sendsa stop signal to ALU circuit 114-x and dynamic counter circuit 116-x.Event logic circuit 90-x also sends a reset signal to flip-flop 124-x,which in turn toggles the match-signal MS-x, and thus the event-signalES-x, from ON to OFF as shown. Because ALU circuit 114-x is in theinactive state in response to receiving the stop signal and will notgenerate a match pulse MP-x, the match-signal MS-x, and thus theevent-signal ES-x, will remain in the OFF state until event logiccircuit 90-x receives a subsequent start-on-assertion IE command.

Force IE Command

In general, when event logic circuit 90-x receives a force IE command,or any variation thereof, event logic circuit 90-x sends a force signalto ALU circuit 114-x, and ALU circuit 114-x responds by generating amatch pulse MP-x, which may toggle MS-x, increment C and trigger saveregisters 106-x. Thereafter, the reference match circuit 88-x may beginor continue operating in accordance with the process shown in FIG. 9.

The present invention contemplates multiple variations of the force IEcommand. For example, in response to receiving a “force-on-assertion” IEcommand, event logic circuit 90-x will immediately send the force signalwhen one of the IE circuits 92-x first asserts the force-on-assertion IEcommand. In response to receiving a “force-OFF-on-termination” IEcommand, event logic circuit 90-x will send the force signal only ifevent-signal ES-x is ON when IE circuit 92-x-y terminates the assertionof the force-OFF-on-termination IE command. In response to receiving a“force-ON-on-termination” IE command, event logic circuit 90-x will sendthe force signal only if event-signal ES-x is OFF when IE circuit 92-x-yterminates the assertion of the force-OFF-on-termination IE command. Inresponse to receiving a “force-OFF-on-assertion” IE command, event logiccircuit 90-x will send the force signal only if event-signal ES-x is ONwhen IE circuit 92-x-y first asserts the force-OFF-on-assertion IEcommand.

FIG. 12D illustrate timing diagrams that show relevant aspects ofreference match circuit 88-x and event logic circuit 90-x's operation inresponse to the assertion of a restart-on-assertion IE and aforce-on-assertion IE command. For purposes of explanation, it will bepresumed that IE circuit 92-x-0 and 92-x-1 are programmed to assert therestart-on-assertion and force-on-assertion IE commands, respectively.

FIG. 12D illustrates timing diagrams for: the match-signal MS-xgenerated by reference match circuit 88-x, the event-signal ES-xgenerated by event logic circuit 90-x, the assertion of therestart-on-assertion IE command by IE circuit 92-x-0, and the assertionof the force-on-assertion IE command by IE circuit 92-x-1. FIG. 12D alsoshows example operational parameters of programmable memory device 86-x,including exception enablement bits IEE(0) IEE(3).

As shown in FIG. 12D, the input exception enablement bits are set to0=OFF except for IEE(0)-1, IEE(1)-1, IEE(0)-2 and IEE(1)-2. With c isequal to either 1 or 2, IE circuits 92-x-0 and IE circuit 92-x-1 areenabled to assert the restart-on-assertion and force-on-assertion IEcommands, respectively. At time t1 IE circuit 92-x-0 receives anevent-signal set to ON in addition to an event-ID that matches theevent-ID in register 96-x-0, and as a result, IE circuit 92-x-0 assertsthe restart-on-assertion IE command as shown. At time t2, IE circuit92-x-0 receives an event-signal set to OFF in addition to an event-IDthat matches the event-ID in register 96-x-0, and as a result, IEcircuit 92-x-0 terminates the assertion of the restart-on-assertion IEcommand as shown. At time t4 IE circuit 92-x-1 receives an event-signalset to ON in addition to an event-ID that matches the event-ID inregister 96-x-1, and as a result, IE circuit 92-x-10 asserts theforce-on-assertion IE command shown. At time t5, IE circuit 92-x-1receives an event-signal set to OFF in addition to an event-ID thatmatches the event-ID in register 96-x-1, and as a result, IE circuit92-x-1 terminates assertion of the force-on-assertion IE command at t5as shown.

Event logic circuit 90-x responds to assertion of therestart-on-assertion IE command by sending a start signal to ALU circuit114-x and dynamic counter circuit 116-x, and by sending a reset signalto flip-flop 124-x. Thereafter reference match circuit 88-x begins tooperate in accordance with the process shown in FIG. 9. During thecourse of operation, reference match circuit 88-x generates thematch-signal MS-x shown in FIG. 12D. The timing diagrams of FIG. 12D aredrawn with the presumption that reference value 720As is greater than orequal to 300 at time t3, and that reference value Ts is greater than orequal to Tm+40 at time t6. As such, reference match circuit 88-x togglesthe match-signal MS-x to ON at time t3, and because the event-signalES-x is presumed equal to the match-signal MS-x, event logic circuit90-x-0 toggles the event-signal ES-x to ON at the same time as shown.

Normally, reference match circuit 88-x would toggle the match-signalMS-x to OFF at time t6. However, because the force-on-assertion IEcommand is asserted at time t4, event logic circuit 90-x sends a forcesignal to ALU circuit 114-x, and ALU circuit 114-x responds bygenerating a match pulse MP-x, which causes the match-signal MS-x totoggle OFF, and as shown, the match-signal MS-x toggles before t6. Thematch pulse MP-x also causes dynamic counter circuit 116-x to incrementc to 2, and the save registers 106-x to capture the reference values inregisters 102-x, respectively.

The S/C-2 bit in programmable memory device 86-x is set to C forcontinuous, which means that reference match circuit 88-x will enter aloop state in accordance with FIG. 9 as described above. The timingdiagrams of FIG. 12D are drawn with the presumption that reference value720As is greater than or equal to 300 at time t7, and that referencevalue Ts selected in step 144 is greater than or equal to Tm+40 at timet8. As such, reference match circuit 88-x asserts the match-signal MS-xto ON between t7 and t8 as shown; event-signal ES-x is asserted ON atthese times also since event-signal ES-x is presumed to be equal tomatch-signal MS-x.

Mask IE Command

In general, event-signal ES-x generated by event logic circuit 90-x ispresumed equal to the match-signal MS-x. However, during the time periodwhen event logic circuit 90-x receives a mask IE command, event-signalES-x may not be equal to match-signal MS-x. In general, when event logiccircuit 90-x receives a mask IE command, reference match circuit 88-xcontinues to operate in accordance with the process shown in FIG. 9.Event logic circuit 90-x, however, masks transitions of the match-signalMS-x from OFF to ON or ON to OFF. It is noted that match-signal MS-xtransitions can be masked even when the transitions occur as a resultof, for example, event logic circuit 90-x receiving a force-on-assertionIE command or a restart-on-assertion IE command.

FIG. 12E illustrate timing diagrams that show relevant aspects ofreference match circuit 88-x and event logic circuit 90-x's operation inresponse to the assertion of a start-on-assertion IE and a mask IEcommand. For purposes of explanation, it will be presumed that IEcircuit 92-x-0 and 92-x-1 are programmed to assert thestart-on-assertion and mask IE commands, respectively. The presentinvention contemplates variations of the mask IE command.

FIG. 12E illustrates timing diagrams for: the match-signal MS-xgenerated by reference match circuit 88-x, the event-signal ES-xgenerated by event logic circuit 90-x, the assertion of thestart-on-assertion IE command by IE circuit 92-x-0, and the assertion ofthe mask IE command by IE circuit 92-x-1. FIG. 12D also shows exampleoperational parameters of programmable memory device 86-x, includingexception enablement bits IEE(0)-IEE(3).

As seen in FIG. 12E, match-signal MS-x toggles at times t2, t3, t4, t6,t8, t10, t11, and t13. The IE circuit 92, however, asserts the mask IEcommand between times t5 and t7 and between times t9 and t12. As such,the event-signal generated by event logic circuit 90 does not togglewith match-signal MS-x at times t6, t10, and t11.

Suspend IE Command

In general, while event logic circuit 90-x receives a suspend IEcommand, or a variation thereof, event logic circuit 90-x suspendsoperation of ALU circuit 114-x. In one embodiment, event logic circuit90 suspends ALU circuit 114-x by (1) sending a stop signal to ALUcircuit 114-x, but not to dynamic counter circuit 116-x, when thesuspend IE command is first asserted by one of the IE circuit 92-x, and(2) sending a start signal to ALU circuit 114-x, but not to dynamiccounter circuit 116-x, when assertion of the suspend IE command issubsequently terminated. Variations of the mask IE command arecontemplated.

FIG. 12F illustrate timing diagrams that show relevant aspects ofreference match circuit 88-x and event logic circuit 90-x's operation inresponse to the assertion of a start-on-assertion IE and a suspend IEcommand. For purposes of explanation, it will be presumed that IEcircuit 92-x-0 and 92-x-1 are programmed to assert thestart-on-assertion and suspend IE commands, respectively.

FIG. 12F illustrates timing diagrams for the match-signal MS-x generatedby reference match circuit 88-x, the event-signal ES-x generated byevent logic circuit 90-x, the assertion of the start-on-assertion IEcommand by IE circuit 92-x-0, and the assertion of the suspend IEcommand by IE circuit 92-x-1. FIG. 12F also shows example operationalparameters of programmable memory device 86-x, including exceptionenablement bits IEE(0)-IEE(3).

Event logic circuit 90-x responds to the start-on-assertion IE commandby sending a start signal to ALU circuit 114-x and dynamic countercircuit 116-x, and by sending a reset signal to flip-flop 124-x.Thereafter reference match circuit 88-x begins to operate in accordancewith the process shown in FIG. 9. During the course of operation,reference match circuit 88-x generates the match-signal MS-x shown inFIG. 12F. The timing diagrams of FIG. 12F were drawn with thepresumption that reference value 720As is greater than or equal to 300at time t2, and that reference value Ts selected in step 144 is greaterthan or equal to Tm+20 at time t4. As such, reference match circuit 88-xtoggles the match-signal MS-x to ON at time t2, and because theevent-signal ES-x is presumed equal to the match-signal MS-x, eventlogic circuit 90-x toggles the event-signal ES-x to ON at the same time.Normally, reference match circuit 88-x would toggle match-signal MS-x toOFF at time t4. However, IE circuit 92-x-1 asserts the suspend IEcommand at time t3, and as a result event logic circuit 90 sends thestop signal to deactivate ALU circuit 114-x. Because ALU circuit 114-xis in the inactive mode, ALU circuit 114-x will not assert a match pulseMP-x at time t4, and match-signal MS-x will not toggle to OFF at thattime. At time t5, IE circuit 92-x-1 terminates the suspend IE command,and as a result event logic circuit 90 sends the start signal toreactivate ALU circuit 114-x. At time t6, reference value Ts selected instep 144 is again greater than or equal to Tm+20, and as a result bothmatch-signal MS-x and event-signal ES-x toggle to the OFF state.

Postpone IE Command

The postpone IE command is similar to the mask IE command. In general,when event logic circuit 90-x receives a postpone IE command, referencematch circuit 88-x continues to operate in accordance with the processshown in FIG. 9. Event logic circuit 90-x, however, masks transitions ofthe match-signal MS-x from OFF to ON or ON to OFF. In contrast to maskIE command, when assertion of the postpone IE command is terminated, theevent-signal ES-x will assume the state of match-signal MS. Match-signalMS-x transitions can be masked even when the transitions occur as aresult of, for example, event logic circuit 90-x receiving aforce-on-assertion IE command or a restart-on-assertion IE command. Thepresent invention contemplates multiple variations of the postpone IEcommand.

Increment Count IE Command

Event logic circuit 90-x may receive and store the maximum event countvalue (MECV). This value may be stored in a register (not shown) ofevent logic circuit 90-x. Event logic circuit 90-x may also include acompare circuit (not shown) that continuously compares MECV with anevent counter value (ECV) that is maintained by event logic circuit90-x. Each time event logic circuit 90-x receives an increment count IEcommand from one of the IE circuits 92-x-0-92-x-3, event logic circuit90-x increments ECV by one. When the value of ECV compares equally toMECV, event logic circuit 90-x toggles event-signal ES-x, and eventlogic circuit 90-x will maintain event-signal ES-x in this toggled stateat least until event logic circuit 90-x receives a start IE command, arestart IE command, or any variation thereof, at which point event logiccircuit 90-x will reset ECV to 0.

FIG. 12G illustrate timing diagrams that show relevant aspects ofreference match circuit 88-x and event logic circuit 90-x's operation inresponse to the assertion of a start IE and a postpone IE command. Forpurposes of explanation, it will be presumed that IE circuit 92-x-0 and92-x-1 are programmed to assert the restart-on-assertion and postpone IEcommands, respectively.

FIG. 12G illustrates timing diagrams for the match-signal MS-x generatedby reference match circuit 88-x, the event-signal ES-x generated byevent logic circuit 90-x, the assertion of the restart-on-assertion IEcommand by IE circuit 92-x-0, and the assertion of the postpone IEcommand by IE circuit 92-x-1. FIG. 12G also shows example operationalparameters of programmable memory device 86-x, including exceptionenablement bits IEE(0)-IEE(3).

As seen in FIG. 12G, match-signal MS-x toggles at times t2, t3, t5, t7,t9, and t11. The IE circuit 92-x-1, however, asserts the postpone IEcommand between times t4 and t6 and between times t8 and t10. As such,the event-signal ES-x generated by event logic circuit 90 does nottoggle with match-signal MS-x at times t5 and t9.

ASC Circuit

With continuing reference to FIG. 1, ASC circuits 33 when programmed,generate event-signals, which are subsequently transmitted to timercircuits 30 via event bus 34. FIG. 13 illustrates relevant components ofan example ASC circuit 33-y. All ASC circuits 33 are assumed to includethe components shown in FIG. 13, it being understood that in alternativeembodiments several ASC circuits 33 may take differing fauns.

ASC circuit 33-y includes an analog comparator 180-y, which hasinverting and non-inverting inputs labeled simply “−” and “+” in FIG.13. The inverting input is coupled to receive an analog reference signalV− from a digital-to-analog convertor (DAC) 182, while the non-invertinginput is coupled to receive an analog sensor signal V+ from a sensor(not shown in FIG. 13) via I/O pad 35-j. Analog comparator 180-ygenerates an event-signal at its output in response to comparing theanalog sensor signal V+ and the analog reference signal V−. The outputof analog comparator 180-y is coupled to an input of a reference controlcircuit 184-y and to pass circuit 194-y. Although not shown, a voltagedividing circuit may be imposed between I/O pad 35-j and thenon-inverting input in order to reduce the magnitude of the analogsensor signal to a level that is in an effective range for analogcomparator 180-y.

Reference control circuit 184-y is coupled to programmable registers186-y and 190-y, which in turn store digital comparator values ViL-y andViH-y, respectively, received from CPU 40. As noted above, CPU 40 (seeFIG. 1) can generate comparator values such as ViL-y and ViH-y as afunction of multibit engine control and/or status values. Comparatorvalues ViL-y and ViH-y are distinct from each other. The values of ViLgenerated for respective ASC circuits 33 may be distinct from eachother, and the values of ViH generated for respective ASC circuits 33may be distinct from each other. Once generated, comparator values ViL-yand ViH-y are transmitted to programmable registers 186-y and 190-y,respectively, via communication path 42. As operating conditions change,CPU 40 may update programmable registers 186-y and 190-y with newcomparator values.

Reference control circuit 184-y selects either ViL-y or ViH-y forconversion by DAC 182-y into analog reference signal V− depending inpart upon the state of the event-signal output of analog comparator180-y. As noted analog comparator 180-y compares the analog referencesignal V− to the analog sensor signal V+. The event-signal output ofcomparator 180-y is either ON or OFF depending upon the analog signalsbeing compared.

In general, the event-signal output of comparator 180-y is ON if analogsensor signal V+ is greater than analog reference signal V−, and OFF ifV+ is less than V−. If V+ and V− are within about 1 millivolts equal,the output of comparator 180-y could be indeterminate. Analogcomparators, such as 180-y shown in FIG. 13, are much like OpAmps, butOpAmps provide a continuous output V out=G(V+−V−), whereas analogcomparators saturate, that is, output an OFF or ON signal. An idealcomparator, like an ideal OpAmp, has infinite input impedance. Thatmeans that it observes the voltage at its input while allowing nocurrent flow. Real comparators are pretty close to this ideal. An idealcomparator has zero output impedance. That means, when it drives itsoutput to ON, it will maintain this output signal regardless of how muchcurrent it has to sink in order to do so. If real comparators are forcedto sink too much current they may burn up, but the output voltage willnot rise more than 100 millivolts or so.

Because the output of comparator 180-y may be indeterminate when theinput signals V− and V+ are within 1 millivolt of being equal, ahysteresis ban can be added to analog comparator 180-y. With thehysteresis ban comparator 180-y, has two important thresholds: theanalog equivalents of ViL-y and ViH-y. Unlike a simple comparator,however, the output of comparator 180-y does not depend solely onwhether analog sensor signal V+ is above or below one of thesethresholds (i.e., the analog equivalents of ViL-y and ViH-y). It dependson both the current state of the event-signal output and the currentvalue of the sensor signal V+. If the event-signal output is ON, it willstay ON until the sensor signal V+ drops below the lower threshold (i.e,the analog equivalent of ViL-y). If the event-signal output is OFF, itwill stay OFF until the V+rises above the high threshold (i.e, theanalog equivalent of ViH-y).

ASC circuit 33-y shown in FIG. 13 also includes an ASC control circuit192-y coupled between pass circuits 194-y and 196-y. In one embodiment,each of the pass circuits 194-y and 196-y may take form in a simpletransistor. The inputs of pass circuits 194-y and 196-y are coupled tothe outputs of comparator 180-y and a programmable register 200-y,respectively, while the outputs of pass circuits 194-y and 196-y arecoupled to event-signal bus 70 and event-ID bus 72, respectively.

ASC circuits 33 including that shown in FIG. 13 are configured, in oneembodiment, to concurrently transmit their event-signal and event-IDonto event-signal bus 70 and event-ID bus 72, respectively, when givenpermission by event bus controller 38 (not shown in FIG. 13). In otherwords, ASC control circuit 192-y generates a pass signal when ASCcontrol circuit 192-y receives permission from event-bus controller 38via command bus 74 that contains an ASC identifier that matches theidentifier stored within programmable register 202-y. Pass circuit 194-ypasses the event-signal output of comparator 180-y onto event-signal bus70, and pass circuit 196-y passes the event-ID stored within register200-y to event ID bus 72 when they receive the pass signal from ASCcontrol circuit 192-y. The event-signal passed onto event-signal bus 72is the output of comparator 180-y at the time when ASC circuit 33-yreceives permission. In one embodiment, event-signal bus 70 and event-IDbus 72 operate in a round robin fashion in which timer circuits 30 andASC circuits 33 transmit their respective event-signal/event-ID pairs,regardless of event-signal state, in sequential order beginning withtimer circuit 30-1 and ending with ASC circuit 33-k.

Example Control Signal

Returning to FIG. 1, control system 10 can generate control signals,such as the spark and fuel signals, as a function of event-signalsgenerated by timer circuits 30. Importantly, event-signals can begenerated by the timer circuits 30 after they are programmed by CPU 40.FIG. 13 illustrates timer circuits and an I/O circuit configured togenerate an example spark signal for controlling coil circuit 16. Moreparticularly, FIG. 13 shows I/O circuit 32-1, which is programmed togenerate a spark signal using event-signal ES-1 of timer circuit 30-1.FIG. 13 also shows timer circuits 30-2-30-5, which are programmed togenerate event-signals ES-2-ES-5, respectively, that are subsequentlyused to control the event-signal ES-1 generated by timer circuit 30-1.

As shown, programmable memory devices 86-1-86-5 of timer circuits30-1-30-5, respectively, store operational parameters calculated orselected by CPU 40. This Figure also shows registers of timer circuits30-1-30-5 and I/O circuit 32-1 that store IE codes and event-IDsselected by CPU 40. SPARK is an event-ID that is stored in both event-IDregister 78-1 of I/O circuit 32-1 and event-ID register 98-1 of timercircuit 30-1, and as a result I/O circuit 32-1 generates the sparksignal as a function of event-signal ES-1 from timer circuit 30-1 usingthe process described with reference to FIG. 6.

The state of event-signal ES-1 depends on the state of match signalMS-1, which in turn depends on reference values transmitted onreference-bus 46. The state of the event-signal ES-1 may also depend onevent-signals ES-2-ES-5 of timer circuits 30-2 through 30-5,respectively, as will be more fully described below. The state ofevent-signals ES-2-ES-5 may depend on the state of match signalsMS-2-MS-5, which in turn depend on reference values transmitted onreference-bus 46. Lastly, the state of event-signals ES3-ES5 may dependon the state of event-signals ES-1 and ES-2.

Timer circuit 30-1 transmits its event-signal ES-1 and SPARK, theevent-ID in register 94-1, whenever timer circuit 30-1 receivespermission from event-bus controller 38. The state of event-signal ES-1may be affected by event-signals ES-2 ES-5 from timer circuits30-2-30-5. In timer circuit 30-1, IE code RST-H, which is mapped to therestart-on-assertion IE command (see e.g., Table 1 above), is stored inIE code register 94-1-0. FIG. 13 also shows DDA is stored as an event-IDin both event-ID register 96-1-0 and event-ID register 98-2 of timercircuit 30-2, which means IE circuit 92-1-0 will assert therestart-on-assertion IE command in response to receiving event-signalES-2 in the ON state from timer circuit 30-2 using the process describedwith reference to FIG. 11. IE code F-OFF-L, which is mapped to theforce-OFF-on-termination IE command, is stored in IE code register94-1-1. MxD is stored as an event-ID in both event-ID register 96-1-1and event-ID register 98-3 of timer circuit 30-3, which means IE circuit92-1-1 will assert the force-OFF-on-termination IE command in responseto receiving event-signals ES-3 in the ON state, and event logic circuit90-1 will send a force signal to ALU circuit 114-1 when IE circuit92-1-1 terminates the assertion of the force-OFF-on-termination IEcommand in response to receiving the first event-signal ES-3 in the OFFstate, if ES-1 is ON at that time. IE code PP, which is mapped to thepostpone IE command, is stored in IE code register 94-1-2. MnD is storedas an event-ID in both event-ID register 96-1-2 and event-ID register98-4 of timer circuit 30-4, which means IE circuit 92-1-2 will assertthe postpone IE command in response to receiving event-signal ES-4 inthe ON state from timer circuit 30-4. IE code F-OFF-L, which is mappedto the force-OFF-on-termination IE command, is stored in IE coderregister 94-1-3. MxI is stored in both event-ID register 96-1-3 andevent-ID register 98-5 of timer circuit 30-5, which means IE circuit92-1-3 will assert the force-OFF-on-termination IE command in responseto receiving event-signals ES-5 in the ON state, and event logic circuit90-1 will send a force signal to ALU circuit 114-1 when IE circuit92-1-3 terminates the assertion of the force-OFF-on-termination IEcommand in response to receiving the first event-signal ES-5 in the OFFstate, if ES-1 is ON at that time. In general, the state of event-signalES-1 equals the state of match signal MS-1 generated by reference matchcircuit 88-1; however event-signal ES-1 is independent of match signalMS-1, and perhaps different, when the postpone IE command is asserted byIE circuit 91-1-2.

Timer circuit 30-2 may transmit its event-signal ES-2 and DDA, theevent-ID in register 94-2, when timer circuit 30-2 receives permissionfrom event-bus controller 38. The S/C bit of line 2 in programmablememory device 86-2 is set to C for continuous, thus reference matchcircuit 88-2 should enter a loop state once it is started. During theloop state, MS-2, and thus ES-2 toggles ES-2 to ON each time the 720angle reference value 720As is equal to or greater than 20, the absolutematch value AMV-1 in programmable memory device 86-2. Event logiccircuit 90-2, however, is configured in this example to transmitES-2/DDA only once each time ES-2 toggles from OFF to ON. Because ofthis configuration, event logic circuit 90-1 transmits ES-2/DDA onlyonce during each cycle of the 720 angle reference 720At, even thoughevent logic circuit 90-1 may receive several permissions from event-buscontroller 38 while ES-2 is ON. Thus, event logic circuit 90-2 simplyignores most of the permissions from event-bus controller 38. IE codeST-H, which is mapped to the start-on-assertion IE command, is stored inIE code register 94-2-0. FIG. 13 shows START is stored as an event-ID inregister 96-2-0. For purposes of explanation only, event-bus controller38, when instructed, concurrently transmits an event-signal set to ONand event-ID=START to timer circuits 30 via event-signal bus 70 andevent-ID bus 72, respectively. Thus, reference match circuit 88-2 beginsoperating in accordance with the process shown in FIG. 9 when IE circuit92-1-0 concurrently receives the event-signal set to ON andevent-ID=START from event-bus controller 38.

Timer circuit 30-3 transmits its event-signal ES-3 and MnD, the event-IDin register 94-3, whenever timer circuit 30-3 receives permission fromevent-bus controller 38. The state of event-signal ES-3 may be affectedby event-signals ES-1 and ES-2 of timer circuits 30-1 and 30-2,respectively. IE code RST-H, which is mapped to the restart-on-assertionIE command, is stored in IE code register 94-3-0. DDA is stored as anevent-ID in both event-ID register 96-3-0 and event-ID register 98-2 oftimer circuit 30-2, which means IE circuit 92-3-0 will assert therestart-on-assertion IE command in response to receiving event-signalES-2 in the ON state from timer circuit 30-2. IE code F-H, which ismapped to the force-on-assertion IE command, is stored in IE coderegister 94-3-1. SPARK is stored as an event-ID in both event-IDregister 96-3-1 and event-ID register 98-1 of timer circuit 30-1, whichmeans IE circuit 92-3-1 will assert the force-on-assertion IE command inresponse to receiving event-signals ES-1 in the ON state.

Timer circuit 30-4 transmits its event-signal ES-3 and MnD, the event-IDin register 94-4, whenever timer circuit 30-4 receives permission fromevent-bus controller 38. The state of event-signal ES-4 may be affectedby event-signals ES-1 and ES-2 from timer circuits 30-1 and 30-2,respectively. IE code RST-H, which is mapped to the restart-on-assertionIE command, is stored in IE code register 94-4-0. DDA is stored as anevent-ID in both event-ID register 96-4-0 and event-ID register 98-2 oftimer circuit 30-2, which means IE circuit 92-4-0 will assert therestart-on-assertion IE command in response to receiving event-signalES-2 in the ON state from timer circuit 30-2. IE code F-H, which ismapped to the force-on-assertion IE command, is stored in IE coderegister 94-4-1. SPARK is stored as an event-ID in both event-IDregister 96-4-1 and event-ID register 98-1 of timer circuit 30-1, whichmeans IE circuit 92-4-1 will assert the force-on-assertion IE command inresponse to receiving event-signals ES-1 in the ON state.

Timer circuit 30-5 transmits its event-signal ES-5 and MxI, the event-IDin register 94-3, whenever timer circuit 30-5 receives permission fromevent-bus controller 38. As an aside, event-signal ES-5 will toggle OFFwhen V1s, which represents the current flowing into coil 16, is equal toor greater than 3. The state of event-signal ES-5 may be affected byevent-signals ES-1 and ES-2 from timer circuits 30-1 and 30-2,respectively. In timer circuit 30-5, IE code RST-H, which is mapped tothe restart-on-assertion IE command, is stored in IE code register94-5-0. DDA is stored as an event-ID in both event-ID register 96-5-0and event-ID register 98-2 of timer circuit 30-2, which means IE circuit92-5-0 will assert the restart-on-assertion IE command in response toreceiving event-signal ES-2 in the ON state from timer circuit 30-2. IEcode F-H, which is mapped to the force-on-assertion IF command, isstored in IE code register 94-5-1. SPARK is stored as an event-ID inboth event-ID register 96-5-1 and event-ID register 98-1 of timercircuit 30-1, which means IE circuit 92-5-1 will assert theforce-on-assertion IE command in response to receiving event-signalsES-1 in the ON state.

FIG. 14 shows timing diagrams of the event-signals and example sparksignal that are generated by the timer circuits 30-1-30-5 and I/Ocircuit 32-1 of FIG. 13. The timing diagrams presume that event-buscontroller 38, at time t0 (not shown), concurrently sends anevent-signal set to ON and event-ID START to each of the timer circuits30 shown in FIG. 13. At time t0, IE circuit 94-2-0 of timer circuit30-2, asserts the start-on-assertion IE command, and reference matchcircuit 88-2, begins operating in accordance with the process shown inFIG. 9. At time t1, reference value 720As is received on reference-bus46 and is equal to or greater than 20, the absolute match value AMV-1 inprogrammable memory device 86-2. Accordingly, reference match circuit88-2 asserts match signal MS-2 in the ON state for a short time. Sinceevent-signal ES-2 is presumed equal to match signal MS-2, event-signalES-2 also toggles ON as shown at time t1. Shortly after time t1, timercircuit 30-2 transmit ES-2=ON and DDA to the other timer circuits afterreceiving permission. Event-ID registers 96-1-0 and 96-3-0-96-5-0 storeDDA, the event ID as stored in register 98-2. As a result, IE circuits92-1-0 and 92-3-0-92-4-0 assert their respective restart-on-assertion IEcommands when they receive ES-2=ON, and reference match circuits 88-1and 88-3-88-5 begin operating in accordance with the process shown inFIG. 9.

At time t2, reference match circuit 88-1 receives reference value 720As,which is equal to or greater than 680, the absolute match value AMV-1 ofprogrammable memory device 86-1. As a result, reference match circuit88-1 toggles match signal MS-1 to ON, and since event-signal ES-1 ispresumed equal to match signal MS-1, ES-1 toggles to ON as shown in FIG.14. Very soon thereafter, timer circuit 30-1 receivestransmit-permission from event-bus controller 38, and timer circuit 30-1transmits ES-1=ON and SPARK to timer circuits 30-2-30-5 and I/O circuit32 via event-signal bus 70 and event-ID bus 72, respectively.

Since SPARK is stored in event-ID register 78-1 of I/O circuit 32-1, thespark signal transitions to ON shortly after time t2 as shown in FIG.14. Because SPARK is stored as an event-ID in registers 96-3-1-96-5-1 ofIE circuits 92-3-1-92-5-1, respectively, these IE circuits assert theirforce-on-transition IE commands, which in turn causes event logiccircuits 90-3-90-5 send force signals to reference match circuits88-3-88-5, respectively. The match conditions MC-1 in programmablememory devices 86-3-86-5 are set to “immediate,” and accordinglyreference match circuits 88-3-88-5 toggle their match signals MS-3-MS-5,respectively, to ON when they receive the force signals. Becauseevent-signal ES-3-ES-5 are presumed equal to match signals MS-3-MS-5,respectively, event-signals ES-3-ES-5 also toggle to ON shortly aftertime t2 as shown. When they are given permission by event-bus controller38, timer circuit 30-3 transmits ES-3=ON and MnD to all other timercircuits, including timer circuit 30-1, timer circuit 30-4 transmitsES-4=ON and MxD to all other timer circuits, including timer circuit30-1, and timer circuit 30-5 transmits ES-5=ON and MxI to all othertimer circuits, including timer circuit 30-1. When IE circuits96-1-1-96-1-3 first receive ES-3-ES-5, respectively, in the ON state,along with event-IDs MxD, MnD, and MxI, respectively, IE circuits 96-1-1and 96-1-3 assert the force-OFF-on-termination IE command, and IEcircuit 96-1-2 asserts the postpone IE command.

At time t3, reference match circuit 88-4 receives reference value Ts,which is equal to or greater than RMV=Tm+5, where 5 is the absolutematch value AMV-2 in programmable memory device 86-4. As a result, MS-4and ES-4 toggle to OFF as shown in FIG. 14. Shortly thereafter, timercircuit 30-4 transmits MnD and ES-4=OFF to the timer circuits, includingtimer circuit 30-1, when given permission by event-bus controller 38.Shortly after time t3 IE circuit 92-1-2 receives ES-4 in the OFF state,and IE circuit 92-1-2 terminates the assertion of its postpone IEcommand as shown in FIG. 14.

At time t4, reference match circuit 88-1 receives reference value 720Asthat equals or is greater than 690, the absolute match value AMV-2 inprogrammable memory device 86-1. As a result, the reference matchcircuit 88-1 toggles match signal MS-1 to OFF at that time. Since thepostpone IE command is no longer asserted, event-signal ES-1 alsotoggles to OFF as shown in FIG. 14. Shortly thereafter, timer circuit30-1 transmits ES-1=OFF and SPARK to the other timer circuits and to I/Ocircuit 32-1 via event-signal bus 70 and event-ID bus 72, respectively.Since SPARK is stored in the event-ID register 78-1, the spark signaltransitions to OFF shortly after time t4 as shown in FIG. 14.

At time t5, reference match circuit 88-3 receives reference value Ts,which is equal to or greater than RMV=Tm+12, where 12 is the absolutematch value AMV-2. As a result both MS-3 and ES-3 toggle to OFF. Shortlythereafter, timer circuit 30-3 receives permission from event-buscontroller 38 and subsequently transmits event-signal ES-3=OFF and MxDto the timer circuits, including timer circuit 30-1. MxD is stored inevent-ID register 96-1-1. Accordingly, when IE circuit 92-1-1 receivesevent-signal ES-3=OFF, IE circuit 92-1-1 terminates assertion of itsforce-OFF-on termination IE command. If event-signal ES-1 was still ON,event logic circuit 90-1 would've issued the force signal, whichwould've resulted in event-signal ES-1 toggling to OFF. However, sinceevent-signal ES-1 was OFF, event logic circuit 90-1 did not send a forcesignal to reference match circuit 88-1.

At time t7, reference match circuit 88-1 receives reference value Tsthat equals or is greater than 750, the absolute match value AMV-3 inprogrammable memory device 86-1. Because MC-3 is set to “greater than orequal to,” both match signal MS-1 event-signal ES-1 toggle to ON asshown in FIG. 14. Shortly thereafter, timer circuit 30-1 sends ES-1=ONand SPARK to the other timer circuits 30-2 through 30-5 and I/O circuit32-1. Even though SPARK is stored in event-ID registers 96-3-1 through96-5-1, transition of event-signal ES-1 to ON will have no effect ontimer circuits 30-3 through 30-5 since reference match circuits 88-3through 88-5 are no longer operating according to the process of FIG. 9.However, I/O circuit 32-1 will transition its spark signal to ON sinceevent-ID registers 78-1 contains the SPARK event-ID.

At time t8, reference match circuit 88-1 receives reference value Tsequal to 500, the absolute match value AMV-4 in programmable memorydevice 86-1. Since MC-4 is set to “greater than or equal to,” bothmatch-signal MS-1 and thus ES-1 toggle to OFF as shown in FIG. 14.Shortly thereafter, timer circuit 30-1 transmits ES-1=OFF and SPARK tothe other timer circuits and to I/O circuit 32-1. Timer circuits30-2-30-5 are not affected by the transition of event-signal ES-1.However, I/O circuits 32-1 will toggle its spark signal as shown.

At time t9, reference match circuit 88-1 receives reference value Tsequal to or greater than 450, the absolute match value AMV-5. Sincematch condition MC-5 is set to “greater than or equal to,” both matchsignal MS-1 and event-signal ES-1 toggle to ON as shown in FIG. 14.Shortly thereafter, event logic circuit 90-1 receives permission fromevent-bus controller 38, and subsequently transmits ES-1=ON and SPARK tothe other timer circuits and to I/O circuit 32-1. Timer circuits30-2-30-5 are unaffected by the transition of event-signal ES-1. I/Ocircuit 32-1, however, transitions its spark signal as shown in FIG. 14.

At this point, reference match circuit 88-1 has entered into a loopstate in which it operates in accordance with the operational parametersin lines 4 or 5 of programmable memory device 86-1. Accordingly, matchsignal MS-1, and thus event-signal ES-1, toggle at times t10, t11, andt12, as shown in FIG. 14. These transitions are reflected in the sparksignal output of I/O circuit 32-1.

Eventually at time t13, reference match circuit 88-2 receives referencevalue 720 equal to 20, the absolute match value AMV-1 of programmablememory device 86-2. Accordingly, both match signal MS-2 and event-signalES-2 of timer circuit 30-2 transition to ON as shown. Shortlythereafter, event logic circuit 90-2 transmits ES-2=ON and DDA to theother timer circuits 30-1 and 30-3-30-5, which results in restart ofreference match circuits 88-1 and 88-3-88-5.

Presuming reference match circuit 88-5 never received reference valueV1s equal to or greater than AMV-2=3 before t13, neither MS-5 nor ES-5toggle to OFF before t13 as shown. However, both MS-5 and ES-5 toggleOFF in response to reference match circuit 88-5 restarting. Shortlythereafter, timer 30-5 receives permission from event-bus controller 38,and timer circuit 30-5 transmits ES-5=OFF and MxI to the other timercircuits, including timer circuit 30-1. Event-ID register 96-1-3 storesMxI. When IE circuit 92-1-3 receives event-signal ES-5=OFF state, IEcircuit 92-1-3 terminates the assertion of its force-OFF-on-terminationIE command. If event-signal ES-5 was in the ON state, event logiccircuit 90-1 would've sent a force signal to reference match circuit88-1. However event-signal ES-1 was in the OFF state at t13, and eventlogic circuit 90-1 did not send a force signal when IE circuit 92-1-3terminated assertion of its force-OFF-on-termination IE command.

FIGS. 14 and 15 and the description thereof, explain how control system10 can generate a control signal such as the example spark signal usingtimer circuits 30. The state of the example spark signal depends onevent-signal ES-5 that is generated by timer circuit 30-5. If ES-5switches from OFF to ON, the example spark signal should switch to OFFif it is in the ON state. As described above, timer circuit 30-5switches ES-5 to ON when reference value V1t, the digital representationof the current flowing into coil 16 (See FIG. 1) is greater than orequal to 3, the value of AMV in line 2 of programmable memory device86-5.

Some control signals, such as the example spark signal, can be generatedbased on the event-signals generated by one or more timer circuits 30.Control signals can also be generated based on event-signals generatedby a combination of one or more timer circuits 30 and one or more ASCcircuits 33. To illustrate, an ASC circuit 33 can be programmed toprovide the same or similar function that is provided by example timercircuit 30-5 of FIG. 14. The example spark signal generated in FIG. 14can also be generated with timer circuit 30-5 functionally replaced by aprogrammed ASC circuit 33, such as ASC circuit 33-1 shown in FIG. 16more fully described below.

FIG. 16 illustrates relevant components of example ASC circuit 33-1 thathas been programmed by CPU 40 with ViL-1=3 and ViH-1=2.8, circuitID=ASC-1, and event-ID=MxI. As noted, ASC circuit 33-1 provides aninterrupt function that is similar to the interrupt function provided bytimer circuit 30-5 of FIG. 14. In FIG. 16, I/O pad 35-1 is coupled tothe output of current sensor 20 (see FIG. 1) and configured to receivethe analog signal that is proportional to the charging current Iprovided to coil 16.

When ASC control circuit 192-1 receives permission from event-ID buscontroller 38, ASC circuit 192-1 instructs pass circuits 194 and 196 topass the event-signal output of comparator 180-1 and the event-ID inregister 200-1 onto event-signal bus 70 and event-ID bus 72,respectively. In other words, pass circuit 194-1 will output asevent-signal ES-5 of comparator circuit 180-1, and pass circuit 196-1will output event-ID equal to MxI stored within register 200-1 ontoevent bus 72. The state of ES-5 will depend upon the analog signalsprovided to the inputs of analog comparator 180-1.

Although the present invention has been described in connection withseveral embodiments, the invention is not intended to be limited to thespecific forms set forth herein. On the contrary, it is intended tocover such alternatives, modifications, and equivalents as can bereasonably included within the scope of the invention as defined by theappended claims.

What is claimed is:
 1. A method comprising: a first register receivingand storing a first digital signal at a first point in time wherein thefirst digital signal comprises a first rotational angle of a crankshaft;a second register receiving and storing a second digital signal at thefirst point in time, wherein the second digital signal comprises a firstvalue of a parameter other than the rotational angle of the crankshaft;multiplexing the first and second digital signals onto a bus; the bussequentially transmitting the first and second digital signals to aplurality of circuits.
 2. The method of claim 1 wherein the parameter isone of temperature, current, voltage, vacuum level, torque, or gaslevel.
 3. The method of claim 2 further comprising: a third registerreceiving and storing a third digital signal at the first point in timewherein the third signal comprises a value of another parameter, whereinthe other parameter is one other than the rotational angle of thecrankshaft; multiplexing a third digital signal onto the bus eitherbefore or after the first and second digital signals are multiplexedonto the bus.
 4. The method of claim 3 wherein the other parameter isanother of the temperature, the voltage, the current, the vacuum level,the torque, or the gas level.
 5. The method of claim 2 furthercomprising: the first register receiving and storing a third digitalsignal at a second point in time wherein the third digital comprisesanother rotational angle of the crankshaft; multiplexing the thirddigital signal onto the bus either before or after the first and seconddigital signals are multiplexed onto the bus.
 6. A method comprising:multiplexing first and second digital signals onto a bus, wherein thefirst digital signal is related to a first rotational angle of acrankshaft at a first point in time, and wherein the second digitalsignal is related to a first value of a parameter at the first point intime, wherein the parameter is one other than the rotational angle ofthe crankshaft; the bus sequentially transmitting the first and seconddigital signals to a plurality of circuits; each of a plurality ofcircuits receiving and storing the first and second digital signals inrespective memory devices thereof; multiplexing third and fourth digitalsignals onto a bus, wherein the third digital signal is related to asecond rotational angle of the crankshaft at a second point in time,wherein the fourth digital signal is related to a second value ofparameter at the second point in time, wherein the first and seconddigital values are distinct from the third and fourth digital values,respectively; the bus sequentially transmitting the third and fourthdigital signals to the plurality of circuits after the bus sequentiallytransmits the first and second digital signals to the plurality ofcircuits.
 7. The method of claim 6 further comprising each of theplurality of circuits overwriting their respective memory devices thatstore the first and second digital signals with the third and fourthdigital signals, respectively.
 8. The method of claim 1 furthercomprising: a first circuit of the plurality of circuits comparing thefirst digital value with a first value stored in a memory of the firstcircuit; a second circuit of the plurality of circuits comparing thesecond digital value with a second value stored in a memory of thesecond circuit.
 9. The method of claim 8 further comprising: the firstcircuit generating a first signal if the first digital value is equal toor greater than the first value; the second circuit generating a secondsignal if the second digital value is equal to or greater than thesecond value.
 10. A system comprising: a multiplexer having an outputselectively coupled to a plurality of inputs; a bus coupled to theoutput of the multiplexer; first and second circuits configured togenerate first and second digital signals, respectively, wherein thefirst digital signal comprises a rotational angle of a crankshaft, andwherein the second digital signal comprises a value of parameter,wherein the parameter is one other than the rotational angle of thecrankshaft; a first register coupled between the first circuit and afirst input of the multiplexor, wherein the first register is configuredto receive and store the first digital signal at a first point in time;a second register coupled between the second circuit and a second inputof the multiplexor, wherein the second register is configured to receiveand store the second digital signal at the first point in time.
 11. Thesystem of claim 10 wherein the parameter is one of temperature, current,voltage, vacuum level, torque, or gas level.
 12. The system of claim 2further comprising: a third circuit configured to generate a thirddigital signal, wherein the third digital signal comprises a first valueof another parameter, wherein the other parameter is one other than therotational angle of the crankshaft; a third register coupled between thethird circuit and a third input to the multiplexor, wherein the thirdregister is configured to receive and store the third digital signal atthe first point in time.
 13. The system of claim 12 wherein the otherparameter is another of the temperature, the voltage, the current, thevacuum level, the torque, or the gas level.
 14. The system of claim 10further comprising a plurality of circuits coupled to receive the firstand second digital signals via the bus.
 15. The system of claim 14wherein each of the plurality of circuits comprise first and secondmemories configured to store the first and second digital signals,respectively.
 16. The system of claim 15 wherein each of the pluralityof circuits comprises a comparator for comparing a digital signalreceived from the multiplexer with a value stored in a memory.
 17. Thesystem of claim 16 wherein each of the plurality of circuits isconfigured to generate a signal if the digital signal is equal to orgreater than value stored in the memory